Help!!!!!!

So I the last period I received was may 7th, I seen a obgyn about 2 weeks ago, pregnancy test negative, and internal ultra sound showed nothing. She said my levels maybe to low to show up but this wold make me about 8 weeks pregnant. Something should be showing up by now wouldn't u think?!

Also have this pain in my lower adomin. I HAVE REGAULR periods so what could be going on?!