hopefully I'm overreacting.

First thing first, I'm not trying to get pregnant. I use condoms very mindfully and I'm not on birth control. Never had a problem before. My period has always been generally normal and I've never skipped a period before. I had sex last on Jan. 6th and my period was scheduled for Jan. 31-Feb.2 ish accounting for some leeway. But yesterday I woke up ate lunch and fell asleep for five hours, woke up still tired and then went to bed. I also have been eating so much more lately but tbh I smoke so I always just thought it was the munchies. With classes starting up I've been feeling stressed and I have gained some weight. So I'm lost. Am I just having normal 20 yo fluctuations or am I possibly pregnant? When's the appropriate time to get a test?