Heavy Period like Bleeding 2 weeks early!

Hello, I am 23 years old and me and my husband have been trying to conceive for 6 months. I had the marina up until 6 months ago and everything went fine after it was removed. All we have gotten is BFN!  :'( I have always been regular with my period. For the last 8 years, I can tell you that I ALWAYS start the first week of each month. Or very close too! Anyways, On August 1st I started and it lasted until August 6th. We had unprotected sex on the 8th, then we both became sick so we didn't do it again until Aug. 12th. This morning the 13th, I woke up with slight spotting. Then it became very heavy like a period. I am not due for my period until Sept 3rd. What could this be? I don't want to take a test unless it is definite that I could be pregnant. I thought maybe implantation bleeding, but this seems to be too heavy for it. Anyone have any ideas what this could be? I have called my dr. but can't get in for another week and a half! HELP!!!