So me and my GF started dating 3½ years ago. About 10 months into the relationship I found out that she had been flirting with one of her exes that reached out to her. When confronted she showed me all of texts and swore that she would never do it again. She blocked his number and as far as I know she never talked to him again. Fast forward 2½ years and I caught her trying to delete texts from a different ex off of her phone. When confronted about this she told me everything that happened. The ex#2 had reached out to her and they were just friendly coversating until ex#2 tried to make the conversation sexual. She told him that she was very happy in her current relationship and that he shouldn't text her. She then proceeded to reach out to him a couple days later and flirt with "light banter" back and forth before she said the conversation just died out naturally. She never said anything sexual to him but my trust has been shattered. This second round of flirting with one of her ex's took place this past October. What really really pains me is that she did this mere days after I took her on an extraordinary birthday date. Swimming with sharks, paragliding, and rented a sailboat for a sunset picnic. I don't understand how me spoiling her on her birthday would illicit her to reach back out to the ex she told to kick rocks just before that. She says truthfully that that day was the best day of her entire life and that no one had ever done something so nice for her in her life. Some friends I have been talking to tell me they have caught their wives and GFs doing the same thing and it was always when things were going amazing. I am curious to see if any of you have had the same experience. Also while looking for answers I came across a lot of things that call it the "life raft". That when a girl perceives a big change coming in her life(me likely proposing to her soon) she will create life rafts just in case things go bad so she won't be without someone if we were to split up. Idk how much I buy that but there were many many posts about it on this topic of GFs texting ex's seemingly at the peak of their current relationship. I don't know what to do anymore she has never given me any other reason than these two to doubt her. I want to believe her that these are the only two instances but I just can't. My gut won't let me. That's why I come here asking you all what you think I should do and also get your take or another's girl take on why she would do this to us seemingly months before I was likely to ask her to marry me. I also cannot stress how much this has made me think that she could have been lying about otherr things and she only told me about this because I caught her.

It's probably also good to note that we sat down and had a 5 hour talk and we laid literally every single thing that either of us had ever kept from the other. This included childhood traumas that we never told anyone else about in our lives. Like shit you take to the grave type things. And many other things that we kept from eachother for one reason or another. This included me telling her of instances of my ex's reaching out to me but me ignoring them and not telling her. I don't have a problem with talking with past partners but when it turns sexual or flirting my belief is that you should immediately stop talking with said person and tell your current partner what happened. I know that I laid everything out there but there is this nagging in my gut and the back of my mind that she is hiding a big one from me.

TL;DR: GF of 3½ years got caught texting and flirting (playful banter nothing sexual) with her ex behind my back. This is the second instance of her doing this the first was with a different ex 2½ years ago. Laid everything out on the table of anything either of us kept from eachother. Gut telling me she didn't say everything...