Hi! Ill try to keep it short, im 18f and my bf js 18m. my bf doesn’t cum at all, only way he does is when i spend around 10-20+ minutes nonstop jerking him off, not by head or sex he just wont, ive made him cum myself 1-2 during 3 years and idk if in doing something wrong or could i do something for it to happen? Or that is just like that naturally. He can get off himself but not when i do it, any tips or is it just like that?