Rash?

So since Sunday I’ve had this rash type thing originally I thought it was an allergic reaction because I get them often but after Benadryl at home AND a steroid shot from the er because it got worse it’s still here. I’m so itchy, I’m washing my sheets and clothes that I’ve worn and I’ve wiped everything down in case something new was brought into the house. Has anyone had something like this? It won’t even calm down with hydrocortisone cream. Also, I’m 22 &6 today so I know there’s not much I can take.