pregnant or no? please help me!

I have Pcos but since May 2016 been having regular 28 day cycles with periods showing up, before may I didn't have a period for 3 years. I had unprotected sex he did egaculate inside me (on 12th August 2016) no period showing up since then at all, taken tests all coming up negative. Had an ultra sound (for only my ovaries, on 9th September 2016) and nothing came up then. Been doing tests since the ultrasound and still negatives! Driving me INSANE!!!!!!! I'm 21, stable & able to have a child. But not knowing what's going on is infuriating x