Male With Constant Nausea Stomach Problems, Help Plz?

Stomach problems, help plz? - male with constant nausea

OK Thats'm a healthy 15yr old man had some stomach problems because of constant nausea last week.I thought of the day, I have a burning feeling in my stomach, I have a sharp pain under my sternum, the burping a lot, and I tons of times I want to eat ima gas.Every vomit. I also have the green chair, and spring break, since I eat junk food only, but recently completed, can you tell me what could be the problem?