Hi OP - breastfeeding is actually really handy for working out what is going on. DD had CMPA and reflux: were told that usually reflux is a symptom of the CMPA but in our case they thought it was both. She also had/has an egg allergy. She was also thriving and putting on weight so we had to do a lot of pushing to get the diagnosis, our main issue was she barely slept at all - they called her a 'happy spitter' I didn't feel that happy about it at 3 in the morning!
What I would advise is: keep a really detailed food diary for a couple of weeks of everything you eat, and I do mean everything. Also record every time she vomits/sleeps/has a wet or dirty nappy/seems constipated/is active/looks uncomfortable/whatever. I resented this but it made me see a connection with dairy and egg, the egg was a surprise (and I really didn't eat much) but basically one day I had poached eggs with brunch and she vomited 11 times.
At that point, I did an exclusion diet. The big issue is, you need to exclude absolutely everything, and it takes about two weeks to be sure its left your body. So I basically went fully vegan (well I kept eating meat but ended up having a lot of vegan branded food as I could 'trust' it), checked long lists of ingredients to be sure there was no dairy or egg derivatives in there. And it still didn't totally solve it, but there was absolutely a difference. At that point (its all a bit hazy!) we were referred to allergy consultant and dietitian, and she was put on omeprazole to help the reflux.
The reason for the initial diary of symptoms is you might find something totally random like tomatoes or peanuts seems to be having an effect, and if its that PLUS dairy and you only cut dairy you might then dismiss CMPA when actually its CMPA plus.
Its a pain to mess around with your diet, but basically the 'goal' once you've identified the allergen and excluded it for a while is to reintroduce the allergens to your diet as soon as possible. Obviously only do all this under advise (though I don't think there's any problem tracking and doing an initial exclusion diet for 'proof') but I was told that they now believe exposing babies to 'trace' amount of allergens as soon as they can tolerate them prevents full anaphylactic allergy developing. In our case, I stayed off egg and dairy till she was nearly one, then I followed the egg and dairy ladders myself- these are quantities and specific foods they suggest to incorporate. It meant that while she couldn't tolerate any dairy directly till nearly 14 months, she had some fairly through my milk from about 11 months, which was really good apparently. Its much much harder (IMO) with formula as firstly there are lots of different types, some babies don't take to them, then you have to start them straight on the dairy directly.