CM intolerance after weaning at 12 mos?

For the first six months of breastfeeding DS I cut diary out of my diet completely and this helped relieve his colic symptoms. After 6 mos I reintroduced dairy and he was fine. At 8 mos he began eating cheese and other dairy products with no issue. So at 12 mos I figured he would be fine to transition to WCM. Shortly after the transition I noticed eczema like rash on his face. Then he became extremely constipated. I saw the NP at our pedi's office and she suggested a switch to soy and referral to an allergist. The soy milk did not seem to improve his eczema. He went for allergy testing yesterday and it came up negative (no allergies). So last night before bed I gave him a little bit of milk. At midnight he woke up and sounded like he couldn't breathe. We took him to the ER and the pedi this morning. To make a long story short he was diagnosed with severe post-nasal drip and his shortness of breath sounds were more him trying to clear his throat. When I get home I google tips for treating post nasal drip and it says stay away from dairy.

So I feel like all signs are pointing to him not tolerating WCM. I guess my barrier is that no one else seems to take this option really seriously (ER gave him milk to help comfort him, daycare, friends, etc - everyone thinks no allergy = no problem). DH is semi on board but both of us are just frustrated.

After reading this board now I'm wondering if soy milk isn't even the best to have him on (it didn't help improve his rash). But the thought of switching to something else has me nervous too.

Any advice on what to try/do/etc. is greatly welcome!!