Formula help / possible allergy??

We’ve changed my little boys (3w) formula from apatamil to HIPP organic about 2 weeks ago as we didn’t think he was agreeing with the first formula, the past week the little babe also seems to be getting worse - throwing up during/after every feed, hasn’t pood in 24hrs, coughing/gagging (silent reflux???) and griping a lot. I know babies are sicky anyway but it’s just seeming to be a lot and pretty thick when he brings it up, he’s also bringing up watery sick. He’s also usually good at going down in his own space but the past two days we haven’t been able to settle him or put him down. I’m unsure if he has a possible allergy and if I should try another formula? I’m going to contact the GP but they don’t have any appointments soon from what I can see. Does anyone have any advice please?x