Why can´t i ejaculate during sex? 10 points?

Masturbating regularly does not impact your ability to ejaculate. Most guys don't ejaculate during oral sex, that is normal. So when you are having sex and want to go ahead and finish, use your groin muscles to repeatedly tighten up your scrotum - like lifting your balls up- and that should cause the ball sack to get hard and tight up against the base of your shaft. That in turn helps kick off your climax and ejaculation.
32 mins ago

no but stress can mess you up

Nerves ??

Masturbation does not cause prostate problems
and should not affect erection in sex.

You are not really comfortable with this girl yet.

Masturbation trains your body to respond to what happens during masturbation. Different body positions, strokes, firmness or soft grip, thrusting exertions during partner sex, and all kinds of differences between partner sex and masturbation can make it tough to orgasm during partner sex that is diffferent from your masturbation techniques.

The simple solution is to use masturbation techniques and body positions that are close to partner sex to re train your body to respond to partner sex better. Not less masturbation. Use masturbation to re train your body to shoot in partmer sex techniques.

Sounds more like you lack chemistry with your partner and/or she's not that great in bed. You're probably causing yourself anxiety during the act by worrying about it.

There are several possibilities.

1. You are sexually exhausted from masturbating.
2. You don't have a foreskin.
3. You are using a condom.