Me and my girlfriend had sex on the 15th. she missed her period sunday and still didn't get it. if she was pregnant would she be getting symptoms?

Possibly not: Many women don't have any symptoms of pregnancy for weeks and weeks. Your girlfriend should get a pregnancy test. It should be positive by now if she is pregnant. Repeat it in a week if she still doesn't get her period.

Possinly: Get a pregancy test to find out. Most people will not get symptoms until they miss their period by more than a week, so the test would be positive before onst of symptoms.