Farting sounds and farting in cl help?

After i eat dinner, i occasionally fart but nothing extreme. Now after i eat lunch in school, my stomach starts to make these grumbling sounds. One sounds like a fart or a fart that is releasing but i hold in my farts because the clroom gets very quiet almost all the time. I ate a cheeseburger, fries, both with not much hot sauce and some chocolate milk at lunch and this happened 20 min. later. The other sound, is like a hungry stomach which also happens AFTER i eat. I don't understand why this happens and how can i prevent it cause it's embarrasing for me.