Why am I vomiting this up?

Whenever I eat stuff with that's sweet like, ice cream, cookies, chocolate, brownies, etc I vomit it up within 10 min. But not all brands of it makes me vomit, I can eat Safeway Select ice cream, and Hershey's without vomiting. And I don't eat it on an empty stomach and I don't eat it when I'm totally full so I'm not overeating. I'm pretty sure I'm not lactose intolerance. Btw, I'm 12, 4'9, 90 pounds, and I was born with eczema