I had sex on dec.28, with a co on and he didn't even finish inside of me. I had my period in jan on tim, but had no period for feb! It's already march now so I missed feb. I'm only 15. I've heard that you can be pregnant and still have a period in some cases !? I don't think I'm pregnant but want to be sure and if I'm not why would I not get any period at all?