I can have the same problem. Sometimes my girl wants to suck me off, and she'll go and go, with no more than a cramped hand and puffy lips for her and a rubbed raw dick for me. It does make me feel bad because I can get her off at will, and word is guys are supposed to be easier but I don't. It sucks because I have great orgasms from head when it happens. Usually if I feel like I won't be able to cum from oral, I try to turn it into full on sex, which is the majority. If it feels right and she can make me cum orally, I let her even at the expense of sex sometimes to give her the 'win' and keep her trying.