He gets soft just before coming

While giving head or doing a handjob, he gets a little soft right before he feels like coming and it prevents him from coming. (He gets hard right after that)

It takes a very long time for me to please him and eventually he doesnt come and uses his hands to come. ( he likes me to touch myself at the time and he says he comes faster if he sees me coming,probably keeps him turned on)

Anyway i could never give him an orgasm without him doing it at the end. I even kept doing it for more than 45 minutes i guess.

He says he is so close to coming but when i do it he just gets more turned on and right when he is climaxing he gets a little soft and doesnt come.

Does this have any reason? Is it becuase he is anxious?