20 & Pregnant?

I am kinda freaking the freak out and need some major advice or help😭 I was supposed to start my period 8 (tomorrow makes 9) days ago. The last time I had sex was October 9 around 2:00 am. I think I'm pregnant bc I've been getting bad headaches/migraines, and peeing a lot more than usual and certain things make me kinda queasy now. Is it too early to buy a test? Should I buy one? What do I do?