I am a woman in her late 20’s, and have a bit of a wild past with incidents of random hookups, with both men and women. My current partner found out about the hookups with a girl and even a threesome and now every time we have sex, despite me telling him it makes me uncomfortable, he asks for me to talk to him, and tell him about the hookups with girls and the threesomes.
I fear it is the only way he can cum and that he isn’t even thinking about me anymore. Now he also wants a threesome with another woman and I do no,t and it is causing a lot of tension. I have expressed to him why it makes me uncomfortable and the fears I have of it destroying our relationship. Even so, he pushes for it and throws it in my face when we fight. He also guilts me over it because “I’d do it for my ex, but not him”. He also calls me selfish for not fulfilling his fantasy due to my own emotions. Aside from this issue things are close to perfect. I do not know what to do.
LemonVibe 
He isn’t respecting your boundaries. Selfishly using you to fulfill only his sexual desire when its a turn off for you. He is using something from your past to guilt you into his selfish demands.
Oh girl. This boy doesn’t love you. Talk to him one more time as calmly as you can and see if you can get it through his bonered up skull. If you can’t, move on. You are not a sex toy just there to pleasure him.
Enthusiastic consent is the only way to go. He is being pushy and selfish which should show you his true character. You are not you’re past and if he can’t accept that trying those things again is not what you want than he is not worth being around. I’m so sorry he’s using you like this