Can't give him a blowjob

My boyfriend and I have been together for 8 months and I still haven't given him a blowjob. I know it's messed up because he eats me out and fingers me. I just can't bring myself to do it. Every time I was about to I just can't. His dick is a lot smaller than what I'm use to so I'm not sure how to do it with a small dick. And the last guy I gave a blowjob too was forceful and made it bad and like pushed my head down so I have a negative look on it. What should I do