Check if he has fever or not to exclude bacterial or viral infection or even cold can cause this . .
Bless him

@chesscalouise2 I haven't even registered him at the docs yet :/ I don't understand how he's been perfectly fine and all of a sudden this has come on? xx

sounds like reflux too me make a doctors appointment they will give you some reflux in the mean time keep him up right as much as possible both my kids have had it xx @jessyab

@mother_of_humans tried burping him regularly on his last one but when I stop to burp him he doesn't drink any more, normally he drinks a good 3oz and up until today kept it all down, but his last feed where I burped him a lot he only drank 1oz. Has managed to keep it down so far though.
Thank you for your advice! Can't help worrying haha xx