You may have a haiatus hernia. Don't panic, it's very common, and you can be born with it, so don't worry about getting one at your age. Haver a word with your GP who may refer you to the hospital for a barium swallow. They ask you to drink something like a heavy milk-shake, and then x-ray you as it passes through your system. If it's serious, it's simple surgery, if not, then medication will keep it under control, but either way, a GP visit is in order to see what's going on.