Are you stressed at the moment?
I've been feeling like that for about a year. Felt sick after a couple of mouthfuls and then afterwards too. Sometimes I wouldn't eat because at least I wouldn't then feel sick. But then not eating would eventually make me feel sick.
Spoke to a friend who said she often felt the same and she said she thought it was stress related. I've never seen myself as someone who gets stressed but after the conversation I had with her I sat down and had a long think. And since then I've made a conscious effort to not get worked up about things, take the back seat sometimes and just slow down a bit. I've now done a full week without feeling sick and I'm hoping it's going to continue.
When you do get nauseous I find Green Tea is a great help.
Hope you feel better real soon