guys like blowjobs... right?

My boyfriend and I were having sex yesterday, but he's got quite a bit of stamina and I was getting sore, so I suggested I give him a blowjob while I recover. I quite enjoy giving head, and he seems to REALLY enjoy it, but I much prefer slow, teasing oral, sometimes dragging it out for an hour or so (not teasing him, just not bringing him to a climax until the end). We were at about 30 minutes when he asked me if I wanted him to jack off onto my chest. I said alright, but when he tried very, very little came out (which is really unusual for him). He told me that happens when he's too sensitive, but I'm a little embarrassed. I offer him head a lot because I (have been taught to) think it's a really nice surprise for a guy. I'm worried that he doesn't actually like head, or that I'm just not good at it. Any advice?