giving head

I give my bf head on a regular, just about every time we have sex. I don't like giving head but I know he likes it so I do it for him. Recently he's asked me to do a little more when it comes to oral sex and I obliged even though he knows how I feel about giving it. But now he's trying to get me to do even more stuff and I'm really not feeling what he's asking. He's says it's not a big deal but what do I do?