Am I over-reacting?

Hi all

I am in a relationship with my gf for about 9 months. I have known her through a dating app and after meeting up regularly for a month or two, we got together. We shared our past so we knew what we were going for, I had no issues with it. The main thing is that she had a few flings (casual sex involved) with one or two friends in school and another one or two through the dating app before she met me and of course she had a few relationships as well. I do not see all these as a problem, but I always had an issue with her keeping contact with them (her argument is that if she didn't initiate the conversation and she knew where to draw the line, its fine). I accepted it then.

We always had teething issues which we always feel our own views are right and that the other party was wrong. And because I do not wish to hurt her (she will mostly get very angry, sometimes end up crying) whenever we quarrel, I will give in to her and apologise (when girls cry I will feel very bad).

Recently, I found out that one of her fling, lets call him Guy A, from school has been contacting her since the very day we got together. And Guy A still constantly trying to get her to meet up (even late at night he ask her if she is free) and even "sort of" imply that it's ok if she didn't listen to me. Yes my gf constantly rejects me but when I read the conversation, there was a few issues I cannot let go.

1) She told him things that are, to me, personal (asian culture). Sometime back when we were together for maybe 2 months, she had forgotten to wear her bra out when she went to work, only to realised it when she was already on the train. She did tell me she told a few of her girlfriends which I understand, but what I found out was she also told Guy A. I asked her if she thinks its ok, and she thinks it's perfectly fine because she said she was just casual texting and she would tell anyone whom she was talking to at that moment and just so happened she she was talking to Guy A.

2) Before whatever happened in point 1, something else happened. We were having dinner together, her phone was on the table, a text came in, she immediately subtly took her phone and kept it in her bag. But I managed to saw the Guy A's name on it. I didn't confront her until a few days later because I couldn't grasp why she was doing that. Her response was that it was her natural reaction and he was just asking about her itinerary for her recent trip. She also got mad and told me that she has some close male friends in school but now she can't talk to them because I am over possessive and easily jealous. I apologise gave in because I think at that point of that it was nothing much. At that point of time, she conveniently left out that this is Guy A whom she had a fling with.

3) My gf couldn't answer me when I asked her what is the reason for her to keep in contact with Guy A knowing that he has so many ill intentions? Furthermore he keeps saying stuffs like you don't have to listen to your bf, sort of like "belittling" me. Her responses is "I know what kind of person he is, and the important thing is I know when to draw the line", that she is already "politely" declining all his requests. She is not even answering the question.

4) After all the explaining to her, she still doesn't get my point. She thinks that she did nothing wrong here and that it is ok to still keep in contact with Guy A. But my point is that I am trying to convince her that this is all wrong.

- Why is she still talking to Guy A when he is already belittling me? Why is she not even defending me to Guy A? In fact when she said "I know what kind of person is he", to me that sounds like she is defending him.
- I am so furious because she thinks she did nothing wrong and even wanted to break up with me because I am so insistent. To me, it is already wrong right from the start when she decided to contact him and even more wrong when she still kept in contact with him after what he has said.
- I as a guy feel angry, because I feel that she is leading him on to nothing, she is teasing him, giving him hope out of nothing. Just for timeline sake, he has been talking to her since last year November up till now. I have never seen a guy so patient before. I feel that when she told him about her not wearing bra so randomly, it was so suggestive. It already gives any guy that hope, what more about the ex-bfs or ex-flings?

So after everything, am I really over reacting? Or is it normal to tell someone you haven't talk to for a long time that you forgotten to wear your bra to work? Is it normal to continue to talk to your ex-fling knowing he still wants to get in bed with you even though he knows you are attached? How can I convince her that she is wrong?

Is she right? Because I am so angry, I can't give in this time even if I want to. Because I feel that if she tell me this is ok, and even if I get her to stop talking to this guy. Next time the same thing will happen again, just different scenario, different guy, different story but the same idea. It hurts so much for someone I put in so much effort into, do this to me.

Thanks for reading my long story. Hope to hear some inputs from everyone!