Suggest Treatment For Dizziness With Nausea And Vomiting

Hi, when i walk up alot of stairs, and get slightly winded, i suddenly am very away of my belt and its pull on my stomach. When I think about it, i get nauseous. Is this all in my head? Could me being out of shape cause this? It it never causes me to vomit, but it does make me very uncomfortable. I can do normal phisical activity, and can do most excersizes. This only happens when i'm walking. Male 20 225lbs 5' 11''