Cows milk or goats milk?

My 1 year old has just been a complete mess the past few weeks. He started waking up in the middle of the night, naps literally half the day, is extremely constipated and just overall fussy and miserable. We can’t figure out why all this is going on even after seeing his doctor. She prescribed him an iron supplement because his irons low (also makes the constipation worse 🙄) but I’m worried that won’t be enough to help. He’s drinking cows milk but Would switching to goats milk be beneficial for him? Also she talked about maybe getting him on DHA and probiotic supplements. It’s just a lot of new stuff so I’m a little overwhelmed and I’m not sure how I feel about all the supplements.