Blowjob help

I need some advice. I’ve been seeing this guy for a little bit and when we have sex, he goes down on me but I don’t always return the favor. He mentioned something the other night about it. It’s not that I don’t enjoy giving him head, I just can’t stand the taste of cum. It literally grosses me out and I gag just thinking about it. I didn’t tell him the reason I don’t do it. How can I get passed this?? Should I tell him my reasoning for not giving head often?? Any and all advice is welcome!