Thanks for the replies. I only gave food at breakfast yesterday and then he just BF all day. After his bath he did a huge poo and seemed much happier for it. Am going to just do food in the morning and lunchtimes for a bit, see how it goes.
No idea if it would work but I read that it's best to feed earlier in the day to start with, so give him lunch rather than supper. Then he might get over any digestive issues before bed time.
My dd got constipated on the same food you are giving your DS. Do keep an eye on it. With dd I had to stop weaning for a few weeks and try later, as she didn't poo for 10 days! But when I tried again later everything went fine, the HV said perhaps dd's digestive tract had matured.
What are you feeding him? If it's nothing "milky" then I doubt it it'sfrom the intolerance. Are you offering him a bottle anyway or have you drop down the dinner one? some kids get fussy missing the dinner bottle for a while...