advice.

Hey gals. So I need some advice. I can't make my man cum when I give him head. He says it feels good but he won't even let me go long enough to make him cum. He like pushes me up and when I tell him I want to keep going he just says no. So I don't think it does much for him... is there anything I'm doing wrong? Any tips? Can I tease him? How do I tease him? I need tips from a girl who does this to her bf!!!!