March 25 I had unprotected sex twice. (same person) 2 days later I got my period and it was way shorter and lighter than normal. It ended around the 29th. My period normally lasts a week and it has always been consistent. Yesterday. I woke up with mild cramps and brown discharge in my underwear. My next expected period isn't until the 24th of April. What could it be?

It could be 100's of things, and there is no way to know if you are pregnant at this point. Of course you could be since you had sex. But you will have to just wait, wait to see if you miss your period, and if you do miss it, wait another two weeks to do a pregnancy test