Nausea , bloating and gas cramps

I am a 17 year old female and I am very active. I am on drill team and practice for at least 2 hours per day. I usually eat a small breakfast either oatmeal or cereal and for lunch i have a sandwich and chips with a water and snack throughout the day because I am hypoglycemic. I usually eat whatever my mom has made for me. Everytime i eat anything more than a few bites of something, i become nauseated and bloated and have bad gas cramps. What could this be???