Not tolerating cows milk

I started making the switch from formula to cows milk this week with my 11 month old. I've been doing 1/3 cows milk to formula 2x per day (he has 2 bottles, morning & night). He's not tolerating it though. The last 2 days he's pooed up to 6x and they have been very watery and created nappy rash. He's also very unsettled and I'm guessing having tummy pains. I'm going to give him a rest and go back to 100% formula until he's feeling better and then maybe try rice milk instead. (any other suggestions welcome!).
Just wondering if anyone else has had trouble with the switch? Has it been a permanent thing? i.e. they never tolerate cows milk? Or does he just need longer for his digestive system to be ready for it?
I switched DS1 over cold turkey and never had a problem, so this is new to me.
Also, DS2 has always suffered from low grade ear infections and since starting the cows milk he seems to be pulling at his ears again. Coincidence or something to do with the cows milk? Poor little guy. I just assumed because formula contains milk proteins that there would be no problem.

Hm, I would have thought the same if the formula is a dairy-based one? He would have already been exposed to plenty of dairy proteins. The ear infections could be an indicator of an intolerance, though.
I don't suppose he could be unwell from some other source? Perhaps it would be good to get some medical guidance - a dietician who specialises in children, perhaps?

Hope his tummy is better!

My DS was quite spewy with all things lactose and it took until about 14 months for him to keep milk down. Even now I don't really give him too much milk, I give him his calcium in other forms which he seems to tolerate alot better than milk for some reason. The one thing that I wanted to say is to consider very carefully using rice milk as a substitute for milk. Everything I have read has said that rice milk is not of any nutritional value to a child under the age of 4.

Yeah, at 11 months he's probably still getting a lot of nutrition from the milk, so better to stick with formula in any case, probably, then once he's eating more - adn getting more nutrition from other sources - you can introduce whole milk - cow's or other - as part of the diet (so, glass or two, not masses of it). Does that make sense?

Thanks guys. It's been 24 hours now of 100% formula and his poo's have sorted themselves out already. Obviously his little tummy is not liking the milk. I'll stick with the formula for another couple of months and then we'll give it another go. He's a pretty sensitive little guy and everything so far has been a very slowly, slowly approach. I guess this is another to add to the list :)