Please Help

Okay so my boyfriend will go down on me a lot because he enjoys it, but I don't like giving blowjobs... I've done it twice and I just don't like it at all. I told him that I would do it on special occasions, but he still tries to pressure me to do it sometimes. He'll even pull the "I did it to you" I try to tell him no but I just feel like I'm being awful for doing so. He's told me before that he won't make me do anything that makes me uncomfortable, but yet he keeps trying to get me to do this? I don't know what to do.