Had the stomach flu 5 days ago and since then i feel nausea when i eat. keep losing weight because of it. is this psychological?

Probably not...: Since the stomach flu was only 5 days ago, the ongoing nausea is probably just due to residual inflammation. Resume eating very bland and easily digestable foods. That said, one can develop a psychological aversion to foods you actually vomited. If this is the case, avoid these foods temporarily and gradually the aversion will fade.