9 days of bleeding after already having a period

I am on the pill and I had my normal period off the pill and after my "7 days" grace i started back onto the pill, when i started back on it i had some really bad cramps and then a week into my pill i started spotting and i did not miss a day. The bleeding was first a bit in a discharge and spotting and then for 5 days was a heavy heavy period like i have never had before and then it went light again. I have now been bleeding for 9 days. There is also a smell to it as well. I took a pregnancy test when i first spotted and it came up negative. I have had sex during these 9 days of bleeding. is it possible to be pregnant when i have no symptoms and have been on the pill? Could this be a side affect of an std or something more serious or some sort of infection? Its the long weekend and all doctors offices are closed and the cramps are so painful, please help if anyone has had symptoms like this before