2 periods in a month??

I had my normal period at the beginning of the month and recently started hooking up with a new guy after. We had sex around a week after I finished my period. We used protection for most of the sex but I was a bit stressed that I could've gotten pregnant. 2 days later I started bleeding heavily and basically had another whole period. 3 days period free I bled again for an entire day and then magically stopped the next day. I have been under stress as I have a big business trip coming up & because of the "could be pregnancy" scare. Any opinions on what could be the reason for this would be greatly appreciated.