He doesn't like giving head

I've been with my boyfriend for 6 months now and I think he doesn't like giving me head. After I give him head he either says I'm tired or I have to ask him for it and he says I'll do it tomorrow. When he does give me head he down their for like a min and then his down. I know it's not me because I make sure I take showers at night and in the day time. I really don't know what it is?? But can someone help me? Is it just because he doesn't like it. Also I have ask if he doesn't like giving me head and He says I do. Again someone please help me understand why he doesn't like it. Should I stop giving him head to show him that if you don't give it you won't resive it