I would like some advice or just a different outlook please. I have been involved with 3 guys "seriously" in my life and they have all gone wrong because of the guy's behaviour.

First guy: We dated for a few months when I found out that he had a gf. I cut him off and a few years later we started talking again. We got really close and I lost my virginity to him. I later found out that he had a gf and I was a side chick. I cut him off for good and never heard from him again although when he was drunk one night, he  told my best friend that he felt bad for what he did to me.

Second guy: We met in our home country and started talking but it was just friendly. I returned to the UK to complete university and he came up as well but In a different city. We then got close and began dating.  A year later I returned home and we did long distance but about a month after I returned home, we broke up. My friend sent my screen shots of him asking her for sexual favours and when I confronted him, he acted like it wasn't a big deal and still wanted to be in a relationship. He acted like he did wrong and like nothing happened so I cut him off.

Third guy: We had a great relationship or so I thought. Everything was good with us and I cared and loved him in a way that I didn't for the others. He has depression and would act out here and there but it didn't really affect us until recently. He started to emotionally abuse me and blamed it on his depression. I would always ask what I did and he said it's nothing to do with me but yet continued. He would ignore me, put me last, neglect Me, be rude and disrespectful and distant on a whole. He intentionally did this stuff and when I called him out on it he did nothing to change it. I continued to stay and tried to make it work by being there for him even though it took a toll on me and made me lose alot of weight and I was stressing alot. He knew he was hurting me yet he continued until we broke up.

I'm wondering if there there is something about me that made it so easy for them to knowingly hurt me and just didn't care about it? I never gave them a reason to mistreat me so why couldn't they care about me the way I cared about them? I've always been what I consider to be "good" to them. I show them love, care, concern and give help when needed.  I put them first and we were so close that they introduced me to their mothersand family. However they had no problem hurting me and throwing me to the side like I wasn't good enough. I'm now wondering if there is  something about me that I need to change so that this treatment will stop??