Increasing nausea....

So AF was a week late and now that AF has arrived (really light compared to normal) , I've been feeling weird. I've been extremely nauseous and lightheaded, having back aches and headaches like crazy, and having hot flashes every morning. I'm super sensitive, finding myself crying like once a day and I'm always exhausted... This has never happened during AF like ever. Usually, I just get slight cramps. What's really going on? I can't be pregnant if AF showed up...

Any suggestions or has anyone gone through the same?