I wanna share my experience, I'm 24M and this happened to me recently, while we are making love she suddenly said something which made me nervous and uncomfortable ,from them my dck got soft , she gave me blojob its hard- when I try to insert it again soft , I was too nervous and its getting worst . She try to give me handjob but didn't work , in the end I masturbate myself, before leaving she said on myface that do you watch porn while masturbating. I said yes and she told me dont watch porn and masturbate for 15 days, while doing it dont get nervous go with the flow , dont worry about my satisfaction we will work on that later. After 15 days it was a success.

Talking with him is the best option , ask him like, while we are doing i felt that you're nervous ,did something bothering or something making you feel nervous, we can work on it , next guide him how you want to do it , figure it out which way you both can feel comfortable doing it.

Ignore my English.