What Causes Severe Nausea, Stomach Ache And Headache In The Morning?

My 21 yr old son is waking up very early (about 5:30 am) with extreme nausea and stomach aches and a headache. He said it feels like a hangover, but has had no alcohol. It wakes him up. He can barely tolerate water and then when he s up, a bit of banana. He can t stand the smell of anything. As he gets up and showers and goes to work, it eases off. He has normal bowel movements, no diarrhea, no bloating, no gas, no fever, no dizziness. It s been going on for 5 mornings. No change in diet or lifestyle. He was in Lesotho, Africa for 2 months at the end of 2016 on a flight internship. Could it be a parasite from Africa? He did have food poisoning just before he left Africa, plus he ate all kinds of local/street food. He looked so awful at work this week that a co-worker said he looked as if he d just gotten out of a Mexican prison. Any idea what it could be?