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To me, since you said this is not intentional, it sounds like there's something medical going on here, whether rumination disorder or something else. I don't think food coming back up after meals frequently is something that everyone experiences. It would be different if it was something that happens once in a while, but it sounds like this happens pretty often for you. It doesn't sound like something you WANT to be doing and does sound like something that is causing you unwanted problems in your day-to-day life.

Are you able to ask your parents to take you to your primary care doctor? You can tell your primary care doctor how long the symptoms have been going on and exactly what happens. If you notice it happens more often or worse after eating certain types of foods, bring that up too. Does it happen more often in times of stress, or does it happen pretty much all of the time? Does it happen with every type of meal, or only some (for example, does it happen mostly at dinner or does it happen with every meal)? These pieces of information can serve as clues for your doctor. Let your doctor know how it is affecting you, like how you said it's hard to sing or talk after it happens. If there are any other symptoms that you've noticed, such as stomach pain, nausea, appetite issues, or something else, bring that up too. You can even bring up what you saw about rumination disorder and see if it fits for you.

Your doctor might want to run tests on you to rule out any medical causes. Or, they might want to refer you to a gastroenterologist (GI doctor). A GI doctor deals with the human digestive system, so they'd be the experts in this area.

If they find out there's nothing wrong, at least you know! But it's better to be checked out and told there's not a problem, than to ignore it and find out the hard way that there is something going on. It might give you some peace of mind to just get looked at. I don't think you're attention seeking at all, and your concerns are valid.

I wish you the best of luck if you do decide to get it checked out!