Does anybody know what this could be?

Okay so I put up a post about this about a months ago. Last month I had three periods and spotting in between so basically I bled all month. I did go to the doc and had a pap and everything was normal. I took a pregnancy test a little over two weeks ago it was negative. Has this happened to anybody else? Also I have had symptoms of being pregnant, nausea, tenderness of the breasts, cravings etc, However the test was negative.
I do not use birth control. This has never happened to me before.

About Tyra Everest
Current: Farmington, New Mexico
Birth: July 20
On since: Mar 30, 2014
a stay at home mom, I don't really have any hobbies. I was going to College full time, but since I had my second child I have not had the time to go back. I would like to change my major, for Veterinarian. I am planning on going back.