Why do I wake up every morning extremely nauseous?

I'm not pregnant that's for sure. But every morning I can barely get out of bed because I feel like I'm going to throw up. I have to take prescription Zofran just to ease my stomach, but even that doesn't always work. Could it be anxiety? I HAVE been stressed out lately, but this has been going on for about 6 months now. And my stress hasn't been debilitating, I can function fine and I don't freak out about things. Any ideas?