13 month old dairy sensitivity

Throughout infancy my son was put on non-dairy formula because he had severe constipation with regular formula. He switched to gerber soothe around 9 months per his doctor which has dairy but he did great on it. Hitting 1 we tried whole milk at first assuming he grew out of the sensitivity. His constipation quickly came back along with fever every other day and a rash on his face, stomach and back. So we quickly switched to a dairy alternative, Silk Almond Milk. He did great for the first few days, his bowels were back until about a week taking it when he began pooping 4-5 times a day. After 2 days of that he developed a diaper rash from all the wiping. We’re on day 2 and on top of the diaper rash he has had 2 blow outs - pools of diarrhea that have come all the way out of his diaper and he vomited this morning while eating breakfast. Is he allergic to the Almond Milk as well? He only gets 2 8 oz bottles of it a day - a morning bottle and a bedtime bottle. Please, please advise. I’m still waiting on his insurance to be renewed since he just turned 1. I’m very close to just paying out of pocket for him to be seen because he cannot catch a break!