Can Negative HPT While Having PCOS Indicate Pregnancy?

I was wondering if it was possible for a woman with PCOS to have a negative hpt and still be pregnant? I have read several stories online about that happening, but didn't know if it was really valid. I have been on provera and metformin for two years because of PCOS, and haven't missed a period until now. I usually get my period between the 12-15th of the month because of taking provera from the 1st-12th each month. I started running in February, but it did not affect my February 14th and March 14th period. I had unprotected sex on March 24th, 26th/27th, and April 3rd; I know that he pulled out on March 24th and April 3rd. On April 9th I started cramping and had a bit of spotting and brown discharge on April 10th and 11th. I cramped for 2 weeks, and the cramping has now started subsiding. I get nauseous twice a day (in the morning and at night), I have had more headaches, my breasts are more sensitive, I get flushed a few times a day, and have not yet started my period. I have never felt anything like this, so I was wondering if I could be pregnant, even though it was a negative home pregnancy test?