Did I have a chemical pregnancy?

My husband and I were not trying to get pregnant (I am on birth control). But we wouldn't mind if we did get pregnant. About 4 weeks ago, I had my period. It was light and was only 2-3 days. different than normal for me but I didn't think anything of it. 2 weeks ago i had such tender breasts (not like they do when my period comes) But my nipples were so tender you couldn't touch them, and they got very swollen. I got nausea at least ever other day at random times, such as in the morning when i woke up or at night right before i went to bed. sometimes right after i ate. I all of a sudden was very tired too. I went ahead and took a pregnancy test and it was negative (but too early i realize that). I didn't take another one but ive never felt like this before. then this week i was supposed to have my period and it was a little late and I wasn't cramping like i was going to get a period. I was starting to honestly think I was pregnant. Then, this morning i woke up and started an extremely heavy period. I am cramping worse than i ever have before. Now I am pretty dizzy. My friend seems to think it is a chemical pregnancy but I have no idea. Anyone ever had this before??