Id like to break my fear of giving and receiving oral..

First about my past that giving my present a very hard time. When I was 14, I was in a relationship with a sexually abusive guy who would force me to give him blow jobs while holding my nose shut til he came. He would also call me a dirty slut and tell me to wash myself in front of him. He was 2nd guy I had been with and I ended up self conscious about myself. Im 23 now and my bf has been very patient with me. I can suck on him for a bit but I cant stand the taste or texture of cum in my mouth. It literally makes me gag or sometimes throw up. As for him going down on me, he loves it and knows my fear of what goes through my head when he does it and tells me everything positive but I cant seem to fully enjoy it. Like he would be 5 mins in and Id tell him lets move on to sex. When he does it, it feels amazing but the what if game pops in my head and it goes from feeling amazing to no more. I just want to be able to blow him and finish him off sometimes as a nice surprise and I also want to enjoy him going down on me more so any tips or advice would be greatly appreciated..