What Causes Morning Sickness And Nausea?

I have been waking up every morning feeling very sick. It started this past friday morning as a hangover so i didn't think anything of it. Just feeling very blah and nauseas. Sometimes i would vomit and that would make me feel better. Eating also helps me feel much better but i will still have the same sickness the next morning. I have had morning sickness during pregnancy before so i know what it feels like, it does feel similar just not as extreme and i did just have a regular period