8 week old DS started out on bebevita formula from Lidl but was very constipated so under doctors advice we slowly put him onto cow and gate comfort for constipation. He seemed ok on this and we thought now he's a bit older he would be ok on regular formula so over a week we slowly introduced Hipp organic which seems a lot thinner in consistancy and now about two hours after a bottle he will bring up what looks like water with milk lumps in it. He never did this before and I'm wondering if it's the formula but feel reluctant to change it yet again as he's still so young