Hey there, DDCC - DD had a dairy/soy/egg allergy and we had the same issues. She was gaining a ton and nursing fine since nursing would soothe her stomach for a while but eventually would upset it again, so she would nurse again, and so forth. Vicious cycle. I ended up having to cut all hidden dairy/soy and egg out (except for soy lecithin and soybean oil). Something like 60% of dairy intolerant/allergic kids are also intolerant of soy, so it might be something worth taking out as well. With DD, it took about a day or 2 before I noticed significant difference, she was actually smiling and happy more and was not having the horrible crying colic at night for hours on end.
I subbed coconut milk for anything creamy milk (like in mac and cheese - you can't use the cheese packet, but you can use nutritional yeast and garlic powder and it tastes like alfredo!) I subbed Necoa margarine (Earth's Best also has a margarine taht is soy/dairy free) for butter, and rice milk enriched is great on cereal - seriously, I drink it even now that I don't have to have dairy cut out since it tastes so good - I only drink Rice Dream, the other brands taste ricey.
I subbed egg replacer for eggs in baking - you can make tacos without cheese (lots of veggies) and I would make fake cheese with raw cashews ground, nutritional yeast, garlic powder, oil and a bit of salsa. I would throw chicken tenders in the crockpot with a 1/2 can of corn and a 1/2 can of black beans and some salsa and simmer for a 4-6 hours and add some rice and veggies to a tortilla and call it a day - yummy!
You can do pasta (Bertolli's spag sauce in bags is dairy/soy free - check on the others because most have whey in them which is dairy).http://ourgaggleofgirls.com/recipes/
has a lot of good recipes - her creamy sauce is SO good!
Here's some of the recipes I used (this is my blog and I'm a woeful blogger lol)http://waywardscribblings.blogspot.com/
I made mashed potatoes with coconut milk and margarine and you really couldn't tell the difference. Really, if you make things from scratch, it's not hard to go dairy/soy free, but I know how tough it is in the beginning to find time to cook with a new baby. Hope that helps, PM if you need mroe info, I know I have more websites around here somewhere.