What's happening?

July 2017 I skipped a period. It's the only month in my entire life that I've skipped but ever since that happened I found myself feeling nauseous with harsh stomach pains every couple of days again, every single day since then. I honestly have no idea if that has any connection but I just don't know what's going on. Has anybody else had this before? I thought that it'd eventually go away but it's concerning me that it's been over a year without change.