You might be pregnant.
I tried 3 different pregnancy tests before I found one that said yes, and it was right! But I did have the same feelings as you, cramping. My period is always on time, so that was a hint! Good luck if you are pregnant!
I was on clomid with my last pregnancy and I didnt get a positive on any test until a few days after my period was due.. Even those that claim they can tell you 5 days before were coming up negative.. so it is still possible, just give it a little more time, I know its a lifetime everyday you have to wait to find out!!