I'm scared to even kiss him.

I'm paranoid. My trust has been destroyed I guess. I've been lied to by almost every guy I've talked to or dated.
One of the main things is they usually go back to their ex..
Basically every guy I've fallen for still wanted their ex but basically tried using me to get over her. My first long term relationship (lost virginity to him) he didn't still love his ex, but he lied to me all the time, and about 8 months in, he started talking to an ex again. But after that every guy would tell me they were over their ex, I would fall for them, then they'd admit they aren't over her and drop me completely.
-Scenerio I : We met through my friend and I liked him right off the bat. Problem: He had recently broken up with the other girl. He told me he was done with her because she had lied too many times. We hung out and talked for a few weeks, and on his birthday he told me he felt it was too soon but he wished he could just make me his girlfriend. I told him he didn't have to rush anything, but I still gave him sex for his special day. I regret it. A few days later he stopped talking like he did before. His calls became rare. His texts were so few, and so far in between. He finally admitted he was getting back with his ex. I was crushed.
-Scenerio II : I met him at his football game. Again, right off the bat. I kinda was feeling cautious about this one though. He and his girl had broken up a few weeks before he met me. I felt he was trying to make her jealous when we hung out. A few weeks in he asked to have sex and I denied him. He stopped talking to me soon after and I heard through his friend that him and his ex were talking again..
-Scenerio III : I had known him as a friend for a few years. We were never very close but that fall we began texting a lot, and he asked me to homecoming. I knew he didn't want much to do with his ex because she was crazy! We went to the dance and hung out. We went to parties together, he showed me off in public. I was a little more cautious this time though. I didn't take it very far past kissing him for a long time. I started hearing rumors that he was having sex with his ex again so I confronted him. He denied it so I let it go but I still listened and I found out he was lying to me. Needless to say I stopped talking ti him and was hurt.
Now : I am talking to a guy. I reeeallly like him a lot. I trust that he is over his ex, and I trust him. His ex has a new boyfriend. But him and his ex are still really good friends. They hang out and I hate it. I feel like something will happen even though I'm positive he's over her. I'm almost feeling like she will tell him she still wants him. I'm so paranoid to get close. I've barely been able to even kiss him. Does anyone know how to help me get over this? I'm embarrassed to talk to my friends about it. They wouldn't understand. I'm just scared to give myself to someone. After everything that has happened to me, it's so scary.