Feeding help

Ok ladies I’m getting insanely frustrated not with my child but with my mother and my boyfriend who think I’m overreacting. I already contacted her doctor but I am waiting a response but wanted to get help from other moms too.

My doctor recommended a formula change for my 3 month old who suddenly became very colicky and isn’t eating normally, being lethargic, and shaking with fits. Her eating has been decreasing every day now since we’ve been trying to move her to the new formula. She spends most of her time screaming like she’s in pain. I’ve tried gripe water thinking she’s insanely gassy but it doesn’t seem to be working. I do 50/50 with the formula to try and get her accustomed to it and even tried completely switching back to her regular formula just to get her to eat something. She is refusing Pedialyte as well which was my last ditch effort to keep her hydrated since she is refusing to eat either formula completely. Yesterday she only ate about a total of 12oz in a 24 hour period and now today she has eaten only 4oz in a 12 hour period. My mother is telling me this is completely normal and came over to my house yesterday just to yell at me for overreacting and of course my boyfriend sided with her. I don’t understand how a 3 month old only drinking 4oz in a 12 hour period is normal by any means and it wasn’t even 4oz at once. It was 3oz at 8am and 1oz at noon followed by a breakdown. Not only that, but her insane irritability on top of it is also putting me on edge thinking something else is wrong. Someone else tell me I’m just overreacting because I’m about ready to freak out on my mother for calling me insane.