Sudden big change in period?

I've had pretty regular normal periods since I first started. They've changed through the 7 years, but it was gradual. Well here recently I made a big mistake and had a lot of unprotected sex over the course of 5 days, trying to get pregnant. When I got my period I was scared because it had changed so drastically so soon. It went from cramping for two to three days, and breaking out, with a heavy flow for roughly five days, to gradual cramping throughout the day (not bad but annoying in the morning, and getting worse and sharp throughout the afternoon) and spotting/light bleeding/discharge for four to six days. This is the third time it's been like that with the first happening the day after the five day span. I've heard from a few people that it might just be my body changing because I'm still in that age range. Also I'm afraid to take a preg. Test because I've only had a few symptoms and I don't want to get my hopes up. Advise is appreciated!