My 1 year old son seems to be swallowing something from his stomach to his mouth since two weeks ago.it's been three weeks since i changed his formula(pepti to ha) and he seems ok with that.doctor said it's reflux but my son has no history of reflux?

The movement of stomach contents back up the swallow tube either part way or to the mouth is reflux. It can develop at any age & is very common in young (under 4 m) infants. It may produce no obvious symptoms or major pain/discomfort. If so it is labeled reflux disease. It is nice if a simple formula change improved his symptom. It is not clear why you discount the label.