Milk Intolerance?

I need help/suggestions from any of you who have dealt with milk allergy/intolerance. I think we have an issue.

Alex has been drinking whole milk mixed with BM for a few weeks now and up until about a week ago has been doing fine. Then he started throwing up (NOT spitting up) once a day. Originally I thought OK his cough is making him gag and he has a very senstive gag reflex. Monday last week - cough, puke at daycare. Tuesday last week, cough, puke at daycare. Wednesday - home no issues. Thursday - puke - no warning in afternoon at daycare. Friday puke middle of the night. Saturday fine, Sunday fine. Monday no dinner - puke evening. Tuesday puke afternoon. Now my thing is he should be digesting the milk he has about 230 at daycare in the afternoon before his nap. But it was obvious over the last few days he is not based on volume. His OT thinks its a milk intolerance so I got some Soy milk today (although many milk allergy kids have soy allergy as well). His casein blood test came back negative at about 5 months old - but that was pre-drinking milk.

I just dont want him throwing up every day. It is miserable for him and us. Also I cant have him not eating dinner - he wakes up STARVING at 530. Also there is a bug going around daycare but most kids get a 24-48 hour thing - not a week and a half long thing.

Any suggestions?