Dairy intolerant?

I have been giving DS2 cows milk on his weetbix for a few weeks now and he seemed fine. He started swiping DS1 milk cup and drinking it and was ok so I though maybe a little sippy cup in the morning would be ok probably a few mls.
But the past few days all DS2 has done is poo...every nappy change? Its not runny but the only thing different is the milk?
Could this be the reason? He now has a red raw bum :( Its just really odd he would go all the time since he is more they type to go for a few days without going?

What do you think? x

Could be. Could also be teeth? Is he getting any new ones? We had issues with milk, but our problems were solved switching to A2, doesn't work for everyone but worth a shot. :) Other than that you could try a non-dairy alternative like goats milk or rice milk?

yeah could be teeth he has been cutting a few for months now and has been really restless! Will give A2 a try we were drinking it but stopped for some reason? Thanks for replying hun x