Am I Pregnant? :: Light Period, Cramps, Sore Nipples, Some Blood Clots

I use to have irregular periods, but they have become regular over time. I normally have light the first day or two then it becomes heavy and lasts a week. Last month my period was due April 26th, and I ended up getting it on April 30th, I woke up and my stomach was VERY tight, I had hardness under my belly button for a few weeks before period, it was VERY light at first, light pink, and in some mucus. The next day I did not have normal clots like I get which are darker red and heavy. I got these very small light pink clots that lasted a day, and only showed up when I wiped. I had normal clots show up in toilet twice and that is it. The next few days it got lighter, and it stopped on May 4th, I stopped wearing pads on the 3rd day it was so light. I never have periods that light and that short. My nipples are still sore, my stomach still hurts and is a little tight still, have horrible acid reflux, and gas. What could this be? My friend and boyfriend both think I am pregnant, but I don't think I am. I took a test over a week ago and it was a BFN.