Can he trust me again?

ok, my boyfriend and i of a year and a half broke up he told me to get the f*ck out of his life, and i started to see another man, well we worked things out and got back together he was suched a changed man so i thought and i took him back, we texted everyday so he thought we were working things out, we were looking at house and even went bought my engagment ring. and now he says i cheated on him. I don't want to lose him but i've been kissing his a** and he has me convinced that i cheated. i've done a complete 360 on how i look at life and all i want to do it make him happy and get back to normal, but he says he can't trust me and i killed him and he can't get the thoughts with me and another man out of his head. I was completely honest with him about everything even details i didn't have to give, i hide that i dated someone for awhile but then told him. and i need to know what to do, he makes me relive his pain everyday buy telling me i'm a tramp and he's the one that was killed, well maybe if he wouldn't have treated me like a puppet on a string for over a year i wouldn't have gone to someone else. now i'm doing everything i can to earn that trust and make him see i'm not going to hurt him. He says he needs to heal and doesn't know how long and that i have to stand by him and support him and wait till he's ready, and if i tell him i'm giving him time then he tells me i'm running and want someone else when i don't!!!! what do i do?