cumming in sex

My bf swares he cums most of the time but I never see or feel it he has only came like 4 times that I have seen Sence we have been dateing  for 3 years  we have talked about it he said he's turned on and he feels like he is cuming and sometimes when he jacks off he gets soft in the middle of it or sometimes He goes soft in the middle of sex do you think he has a problem anyone have this problem also