What To Do?

This is going to be lengthy. But please bare with me. Here's the dilemma that has been eating away at my sanity for four years now. I've been with my gf for over four years now. There's talk about marriage but I have my reservations to the idea. Here is what main problems are and why I'm so hesitant on the idea.

The problems all stem from the start of our relationship. Still to this day she will not give me clarity on it or the absolute truth. Out of fear it may end our relationship or out of spite. Trust me I've tried 100's of times to get a answer but the stories have changed so many times it would be a impossibility to decipher.

We began dating on the pretense both of us were looking for long term love and ready to settle down. She was 26 and i was 31. All seemed good until I noticed here phone would be going off at all hours of the night. Which set alarms off. I confronted her about it and she said they were just friends. But later I learned they were all guys that she had previous sexual encounters with. I learned one in particular who she had met right before me and had given falacio too. Just two days before meeting me on just their second meet. She had contact with him for the first month and a half we were dating. When she actually asked me after two weeks if we were exclusive. Gives you an idea of her intentions. They were far from what was stated when we first met. Plus it sets tone for her honesty. Now I'll dive in deeper. Here are the main hurtful things she did and won't answer truthfully about.

1st ( The Worst)
This eats me up to no extent still to this day. I'm still unsure of what happened. It was just over three weeks of dating. She came to my house and I hadn't seen her the previous day. She came over and we got intimate. We were in bathroom first and she was sitting on sink. We did the deed and then were headed to bedroom to continue. First i noticed she didn't feel the same as before. I know this because we had had sex for 20 days in row. She felt looser. I really wouldn't have thought twice about it if i hadn't noticed the blood on sink. I knew it wasn't her period. So we got to bedroom and we started to have sex from behind. There's where I saw her anus was actually torn and bleeding. So I stopped and asked her what was wrong. She immediately said she never knew and that she well see doctor.

To actually give you more merit to the story. The guy I mentioned earlier that she continued to talk to while with me. I got this from her too. She said was only into anal and well endowed. So i put two and two together. So after four months from that day of asking, she finally came to some morality on the situation. So her truth was and remember we had been together everyday since we met and intimate every time also.

(Her Excuse)
That when i dropped her off at her place that morning she was so horny that she masturbated both vaginally and anally. To the point she ripped her anus. It gets better. Not only did she supposedly do that to herself. I was like OK, will if that's the fact then were you at least thinking of me? She looked embarrassed and said she was thinking about guy previously mentioned and just happened to send pics of it to him. That was the truth I got! Would you except that as truth?

2.(Demoralizing)
Here's where it gets personal. I never understood body shaming or how it could mess with people as much as they say it does. But it really does and I feel horrible for anyone who has been put through it.

When we first met slowly but surely I saw this woman wasn't what she led on to be. She almost reveled into taking about past sexual experiences. Which is fine as long as your story stays the same. So one night after a couple of drinks, she starts talking about penis size. How she was with two really big guys 8 or 9 inches and one monster of a man. She was proud describing that he was 14 inches. like I literally took out a tape measure just to show her. Her response was, that is how big it was. She even went on to say how she was sore for three days after sex with him. I'm not the jealous type or insecure but just being above average. I had my doubts if I was in her area of likability in the penis department. This all came out within two weeks of us meeting.
So during sex she would say off hand remarks. Such as I'm having a hard time feeling you. So we would switch positions and I would ask her if that's better and she would flat out say no. Which pretty much killed me on the inside. It came to a head one time after a trip to her relatives. We got back and were having sex and she just looked up and said i cant feel you! She had a look as if she was at a funeral. I was angry but tried to keep calm and said has it always been that way and she said yes. I had enough and asked her to leave. She asked why I was upset. I replied your constantly cutting my size down. She then replied I'm misunderstanding. I knew I wasn't misunderstanding anything. I knew this to be true because of past comments. I'd even throw things at her like I'm thinking of enlargement surgery and she would say yes you should, id like that. So having your manhood being dismantled by someone you love is gut wrenching but her excuse for it which i will give below is even worse.

(Her Excuse)
Now after all she has said. She can look at me and say I'm the 2nd biggest guy shes been with. Like I said previously stick to your story! Saying what she says now is like getting slapped in face, it hurts worse then before. She says my size was never a issue. That she would only say that type of thing cause she was mad at me. Which is a lie. Because it was never said during a argument. She also says it was her attempt at pushing us apart. But she always would come back regardless whether asked to or not. Another excuse she says she was so wet while we would have intercourse she couldn't feel the texture of me. Has anyone been told that by somebody who loves them then acts as if its not true?

3. (Feeling Second Best)
This is about one main element in the story the other guy. If not familiar with it please review issue one. So after the whole debacle of whatever happened between him and my gf. I wanted to know why she did whatever she did. I asked her point blank why. May be a week after the whole masturbation story. Story has changed so much its hard to know whats what. Her originally response is what i take for truth. She looked at me that time straight in the eyes and said have you ever met someone that makes your jaw drop. I said yes. She said well that's how he was for me. I said what else. She said he had a bigger penis then I did too and she always thought about the different positions they could do. Figures back to body shaming. That conversation still haunts me. I do believe shes only with me because that guy only wanted f*** buddy.

(Her Excuse)
Now she has a completely different out look. She is a different person now. Her stating he was better looking. Is now just because she wanted to get back at me over something. As for her trying to get with him because he had a bigger penis she was mistaken. I'm bigger now. Would you buy the 360 turn around?

My fault, in reality. I love someone who cant or wont tell me the truth. Out of fear it would end us. I just don't get it never will. If i wasn't good enough then how the heck do you want my hand in marriage. How can someone say and do those things. Only to twist it to the point that no truth can ever be known. I've given myself to someone i don't even know in a sense.

What the hell do I do? I love her but that doesn't trump honesty. I really have been with someone i don't know. I have no idea if I'm sexually adequate or if she cheated on me. Well she did mentally just don't know if it was physical. Would you take someones hand in marriage with so much unexplained baggage.