New at this!

Position, maybe?

We don't even know your gender so we can't even begin to guess re the angle.

I wonder if he/she has this pain after unprotected intercourse.

If it's "in the stomach" - she probably means abdomen - it's probably muscle aches.

If it's in the pelvis area, it could be related to the sex.

She needs to become more aware of her own body and ID body parts accurately.

So obvi from my question it said "protected" and I am a girl. And it's it's my pelvis area only on my left side

Still doesn't tell us much about position (although thanks for the clarification).

It is a form of exercise - have you had an oblique strain on that side?

It was in missionary, that's the only one I feel comfortable with. And I haven't had any strain before, this all is only just new to me! First timer!!

Huh, well there's just the possibility that it's PMS-type ovarian pain. Don't mean to ask you to draw a diagram but that's the first thing I can think of. Unrelated, just a thought as it's the right vicinity.

Maybe talk to a doctor. Certainly a few days of pain is of concern. Just in case it's something that needs to be dealt with quickly, e. g. an ectopic pregnancy, IBS, gosh, there are all sorts of things I could scare you with. To my mind, the issue is a few days of pain. So maybe ask.