I actually think for me morning sickness was always a combination of reflux, hunger, nausea and heartburn.... The only thing that helped was eating salty things constantly. If I got a little bit hungry it would get worse. I was usually vomitting in the morning on an empty stomach - it was awful.

I hope it goes away for you soon, I found week 9-11 the worst, and I read somewhere that's pretty common, but if you are worried it is worth checking with your GP or OB.