Anything But Sex Gets Him There. It's kind of a weird situation.
There's quite a bit of an age difference; I'm 20, he's 44. I only mention this because I've never experienced sex with an older man, and just...it might be relevant. I don't know.

We recently had sex for the first time, but it really didn't seem to do anything for him.  He couldn't get there and after a while wilted.  We tried again but it just kind of seemed like work.

The weird thing is, before I had given him a lap dance and he came after a few minutes. Another time, grinding brought him there.  After sex didn't work, we rested a while, and I touched him a lot and ended up jacking him off very gently and slowly and, lo and behold! He did.  
I've come to the conclusion he definitely likes being teased--touching his neck, ears, nipples, anything really turns him on.  But when we try sex, it's like he's not there anymore.  

Is this completely unheard of?