Shrinking Appetite

My appetite have been shrinking ever since my horrid gastric-nauseous problem last week. I will feel the food taken in at the brim of my throat on the verge of vomiting after every meal. It will take me about an hour or so for that thing in my throat to move down to my stomach. Thus, I am restricting from eating too much which causes me to feel damn terrible after meal. What's wrong with me?