Am I having pregnancy symptoms?

I am on seasonique birth control and have been sick this past month and have been on antibiotics and yes I know that they mess up your birth control. Anyways when my period was expected on the 4th period pill it didn't come.My period always comes on the same pill and lasts for 3 days. The next day I had cramps on and off but only for about an hour with no blood. They next day I started to bleed a tiny bit of dark brown for a day then it stopped. I have had heartburn even when I don't eat anything, headaches, nausea, and not very hungry. Could I be pregnant?