As others have said it could be mental, fear of pregnancy could be the reason, fear of finishing too soon, relax and get to working together he could also have a specific kink that will throw him over the edge. Talk to him
2 Likes
Some good advice there , friend 
1 Like
I had this for years, but I can’t even remember how/why it resolved. Not sure if it helps, but at least I am proof it can resolve
2 Likes