It's strange...

So last Thursday I had sex, it was protected yet when he pulled out after finishing the condom was half in half out. Well i stress extremely easily, and idk what's going on. I have googled alot of stuff and I only get more stressed. I know that you aren't pregnant if you start your period but I started two days early and it was normal and heavy and cramps and clots, but the next day was alot lighter, like not even making it to the pad and idk if it's from stress. I haven't been eating much in these past 3 days and yet I'm still having a very light period. Any one have any ideas?