Why do i get sick during basketball?

When i play basketball, i feel like im gong to throw up. i dont know why. Is it because i eat before games? I tried not eating before it, but i felt sick because i was hungry. Once i had to sit out thats how bad it was. I almost gag!. I really love basketball, but its hard to control the nauseas feeling,. Thanks so much!! also do u have any tips on what food i should eat before, thanks soooo much!