Girlfriend won't do anything sexual that she did with her ex's

My girlfriend of almost 3 years wont do anything with me that she did with her ex's sexually she rarely even makes out with me only pecks. I only get missionary and if I don't cum within a minute of her, I don't get too. It's putting a big strain on our relationship. I was a virgin before we got together and we have talked about it. She said she is scared to do anything but I know it's not that, shes had threesomes (only with another girl and guy) and done a lot of other stuff public sex etc. She promised that she would try more and she still hasn't (that was 10 months ago). I gave her a dead line because I can't do it anymore. She cheated on me (just online chat and really hardcore photos) and after that, thats when I told her I wanted more (all I wanted was a HJ or a BJ if lucky) if we were gonna till be together. I was asking for just your basic nude photo's before and she told me no. every time I bring it up she said that it makes her nervous and that she has to mentally prepare even though I didn't bring it up for 3 months at one point. Sorry about everything being all over the place. I just don't know what to do I love her but with her cheating and not doing things its make my head really messed up and I feel like I can't go on. It also makes me feel like there is something wrong with me which is messing me even more up. I've gotten angry about it and she just cries, If I talk calmly she just agrees and makes promises that she can't keep. What do I do? I really do love her a lot though.

I should also mention 2 weeks prior to her cheating on me we got engaged. After I found out I asked for the ring back.