Part is mental, your nervous and thinking about cumming to fast, just relax, don't think about it, and focus on her. The other part, when you have sex infrequently, you're going to finish fast, that is normal. Have more sex, and that will fix itself once you get adjusted to getting it more often.
If you cum to early, just focus on other things while you get ready for round 2. Kiss her, caress her, give her oral, until you're hard and read to try again.
If you cum to early, just focus on other things while you get ready for round 2. Kiss her, caress her, give her oral, until you're hard and read to try again.