what's going on???????

I've been off of the pill for 3 months now, I got my period the for the first and second month afterwards no stress. But I have had sex with a guy twice during my ovulating period (not planned) on two different days and it was unprotected, but pulled out both times. Now I'm 14 days late and counting, no sign of pms or anything apart from tender nipples, I have done two pregnancy tests between when my period was due and now and both have come back negative, not sure what to think, my friend says I should wait until my next period is due. Has anyone else had this, advice??