Is something wrong

Hey guys, I’ve been having some cramps recently and absolutely no period. I’ve been off birth control since before June and had protected sex but did have a little bit of a slip up. I did take a plan b. I’m 19 in college and honestly nervous that something could be wrong with me. I took two test to rule out pregnancy and both came out negative but I’m still having cramps and no period. I had my period last month but for some reason it didn’t feel right it ended 3 days early( meaning it only really lasted 2 days). I waited it out but now I'm worried that maybe something concerning is wrong me sine my period hasn't come. This has never happened before.