Help save my relationship. I can't help myself.

Hello there. I am making this post to welcome myself to this forum and say hello to everyone. I am proud to make this my first post, and honestly, just signed up to ask this. I want to start off by saying my name is Alexander, I am 15, and I have been in love with my first girlfriend for around 2 months now. She is turning 19 next month. Don't get too scared, I am very mature for my age and hate the immaturity girls my age have. I have had a " girlfriend " before but it was never really serious and only got my first kiss. My first real serious girlfriend which is the one im currently with took my virginity. We have been official for about a week now, and I am happier, but more upset at the same time then ever. I just wanted to fall in love for so long ( about a year ). I didn't ask for all this stress and paranoia. There are minor red flags that indicate she may cheat on me in the future but honestly, there is more indication that she is loyal, I am just super paranoid over all of this. This will be long but worth it I guarantee. Thank you to anyone who reads up to this point and an even bigger thank you to everyone who reads this full post.

I have been with, lets call her Taylor, for around 2-3 months now. I fell in love with her within 3 weeks. I guess you can say she is my first love, but really she is my first everything, other then my first kiss. She automatically denied the fact that I loved her and she dismissed it as puppy love. Weeks go by, we kiss, we have sex, but she still denies I love her. I just wished she loved me the same way I loved her. I tried telling her I wanted her to be my first girlfriend, and she said she didn't want to be in a relationship due to the fact that she was bad with them, Knew me for too little, has been fucked over before in relationships, and that I overall wasn't serious. If she did love me, she didn't show it whatsoever. She did say that she cared about me a lot 100%.

She talked to her mom about me but her mom didn't approve. She said I was too young for her, so now me and her have a secret relationship from her mom, even though her friends know about me. It's important to note she doesn't have much family other then her mom.

Honestly, I can't lie, it did upset me because one thing; She said it was mostly because my age. I can't tell you how heartbroken I was. She is willing to judge me for something out of my control that is passive with little to no impact on me as a person. I couldn't take it.. Call me desperate, but I was on the lookout for someone else who loved me the same way I loved them. I met some girl and was planning on getting with her as Taylor led me on. Taylor found out I was flirting with Jamie, and was devastated, saying she lost all the feelings she has obtained for me in the past couple weeks of knowing each other, saying she thought I was different. I tried explaining to her that all I asked her to do was love me the way I loved her, and that she failed to do that, and that I just wanted someone who made me happy, but she ended up blocking me on all social media for about 2 days.

2 days later, in the middle of the night, I was talking to Jamie and got a text from Taylor. She had told me that she was sorry for overreacting and didn't want me out of her life even as a friend. A couple days go by, and while I was with Taylor over the phone, I sorta lost everything I had for Jamie once Taylor told me she loved me. Is there a reason to not be with her? This is all I ever asked for from the start. So we made it official
( 4.7.16 <3 )

Jamie was upset but understood, and I still have feelings for Jamie and love her low key.

This is not about Jamie though, this is about something else.
Lets go back in time, about the first week I knew Taylor, and the second time I hung out with Taylor ever in real life. I had met her friend, lets call him, John. John seemed like a nice guy who was a friend. Taylor has known John for about 7 years. Taylor was at the mall with him and so was I. When I first got there I hugged Taylor and kissed her cheek. I knew from the second that I kissed her that he had feelings for her. The way he reacted... It was different then most guys. I notice things most people don't. I have been having anxiety attacks ever since this day. I was never really the same. You can say I fear for the worst and overthink things but when I overthink, I am mostly right. I am not a stupid guy, and get told by my teachers I am the smartest student they have had for a while.

Anyways back into the future, 4.7.16, Taylor told me that she had unblocked me on the day that she had sex with John. I knew something was up with her and John 1 day after she unblocked me. She asked me to hangout with her everyday, which was unusual since I would see her 1-3 times a week before and she would see him 2-3 times a week. Anyways back to topic, She had been crying telling me that she couldnt go on with the guilt of lying to me and that she needed to come clean. She defended herself saying that it wasn't really cheating since she had blocked me + we were never together + had no intention of ever talking to me again + was sorta peer pressured into it SUPPOSEDLY. I sorta believe this but sorta have some doubts of it due to trust issues. She told me he had pulled down her pants and she had lift them up and he did it again anyways, and that she left within 30-60 seconds of intercourse. She could be saying this to make it not seem as bad, but honestly, I am just glad she told me the truth. Do you guys think this counts as cheating? I honestly don't, but I really don't know anymore. She told me that she had ignored John for about 1-2 weeks after this happened, until today where she went to his house and talked to him about it. She called me before going to his house and asked me if it was okay. I told her okay even though it was NOT okay and not alright. I just don't want to be that over protective boyfriend, but it bit me in the ass. I spent all day yesterday crying and vomiting. I noticed one thing ; It's not her who triggers my anxiety, It is John. She told me it was super awkward and that she wouldn't ever do anything with him, but I just want him gone. Forever, but I don't want to be that guy who forces his girlfriend to talk to no guys friends. It's just not right.

There are a couple things that indicate that she won't cheat on me : She has promised me she won't do anything with other guys, Knowing that she has been cheated on multiple times, Raped, Physically abused, being raised by a mother who has been cheated on in a marriage twice in a row, do you think that she will cheat on me knowing how messed up it is? She claims that she knows how much I love her now and that I love her. I just need some advice man. I need to be enlightened on this situation as a whole.