Aw mamsh, don't stress, the rashes are probably heat rash o diaper rash dahil sa weather, hindi related sa milk! For mix feeding, okay lang magpatuloy with breastmilk plus formula; maraming mums sa circle ko ang ganyan at walang side effects sa baby, ang importante lang consistent ka at hindi bigla-bigla switching formulas because that can upset their tummy. For formula recommendation with allergies (AD), kailangan talaga mag-consult sa pedia mo para ma-identify kung ano specific allergy ng baby mo, pwedeng lactose-free, hypoallergenic, or specialized formula ang kailangan niya, di lahat ng babies ang same. For the rashes, definitely bring it up sa doctor din kasi almost a month na talaga, they can check kung ano talaga ang cause at prescribe proper treatment. You're doing great, mama, first time mom stress is totally valid, pero the doctors will help guide you from here!