Baby vomitting after feed and has phlegm

Hi there my 6-month old baby vomits always in the morning when he is up. Usually the first week after his long sleep. It can range for just one or two small mouthfuls of spit up and a few mouths. It really depends. If his phlegm is a lot, he sometimes coughs and then will start vomiting. Or when we feed him some solids that he doesn't like, he will gag and sometimes vomit. Though it is usually once (at most twice) a day. Any mommies experience this before? He has some heart condition but this has nothing to do with it. We have also asked a few doctors including a gastro specialist but they mentioned it is quite common and babies will slowly get out of it. He also did a scan when he is 2 months old. Sorry just worried as he already has an underlying condition.#pleasehelp #vomit