2 month old constipation any advice greatly appreciated I'm exhausted!!!

[Smileysar1]

Hi my 2 mth old baby hasn't pooed for 3 days. He's combination fed and currently has 3 formula feeds a day weaning him onto 4 this week.
What could this be?? Wrong formula?
He's screaming and writhing in wind type "poo pains" and looks very distressed.
Anyone got any tips on how to help the poor little fella go? Should I change the formula brand?? Thanks!

Sorry it's been a little while since mine were babies but I'm sure you can give them cooled boiled water at that age can't you. That should help a bit. Also if you lie him on his back and make circular movements with his legs as though he's riding a bike (hope that makes sense) that should help get things moving. My dd3 suffered with reflux and had constipation sometimes (not sure if the two are connected). We changed to 'comfort' milk and she was a lot better with that. We used Cow and Gate. When she was a bit older blended prunes and a bit of formula mixed together worked a treat - but be prepared for a massive poo explosion!