Embarring Nasty Egg Smell ! Why?

I kind of find this embarring, but the last time this happened to me was a couple of months ago in school. when i burp, I'll get a nasty egg smell and it'll burn a little even though i haven't ate eggs. Also it'll stink really badly causing me to have bad breath for the whole day or maybe 2 days and this will occur every 2-3 minutes within the day maybe every 5 minutes if i'm lucky. When I have this problem, the burping is very soundless (not like an ordinary burp where you can hear the person) and it will annoy people around me because they don't know where the smell is coming from. The smell gets mistaken for someone farting, that's how strong the smell is. Also, I'll get pain in my stomach until I feel my body trying to force me to throw up or sometimes i'm on the toilet having bowel movements and throwing up into something at the same time. I know it sounds really disgusting, but i just want to know what can i do to prevent this from happening again? I really can't control it when I have to throw up and I hate it so bad. I don't remember what I was eating at the time, but most times i don't eat things unhealthy since i'm on a diet for high cholesterol for quite some time now. I'm 17, 116lbs.