Mommys , i broke out w this big rash all over my back a couple days ago & its kindaa itchyy . Idk why but theres a bunch…

Mommys , i broke out w this big rash all over my back a couple days ago & its kindaa itchyy . Idk why but theres a bunch of bumps everywhere. I take benadryl to calm the itching & the rash down but idk what it is . It came out of nowhere .. any thoughts on what it could be ? Showed up the day we came home from the hospital i noticed it before i got in the shower , than seen what it was after . It hasnt gone away yet 😕