Helping please my man

So we have been TTC since December and I’ve had my suspicions that my fiancé doesn’t always finish. I didn’t know how to bring it up because I didn’t want to embarrass him. Well, we finally talked about it and he says he has a hard time finishing and brought up his concerns about it hurting our chances of TTC. Does anyone have any experience with this or advice? It’s not just about us TTC, I honestly want him to enjoy it too!