My son was the exact same way - we had him on soy formula from starting around 3 weeks of age due to gas & fussiness. When he was about 11 mo, we started him on regular milk, but found he would have unbelievable blowouts and a ton of gas. We tried soy milk for a while, but it didn't really help much - we now use Lactaid Milk for him - it is expensive, but it has helped him a TON. when he was being potty trained, we actually took all lactose out of his diet completely - including white bread, etc etc - now that he's 5, we allow him to have small amounts of cheese, but still keep him on the Lactaid milk - we can always tell when he has too much lactose - he's in the bathroom a lot! Swiss cheese has the least amount of lactose in it, so its the safest cheese for them to eat.
Giant Eagle sells the Lactaid Milk - we buy it by the gallon, which is close to $6 for one gallon (but is cheaper than buying a half gallon at a time) - the expiration date is always pretty far away on it, and Giant Eagle will have a sale on it about every 6 weeks, where it is about $4.30 or so - the more you buy it at Giant Eagle, they will start giving you coupons for $1 off a gallon, which I use when its on sale.
hang in there - you just have to be careful what you give her, and eventually it will just become a normal part of your routine.
God Bless!
~T.
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