Uti infection for the second time and the cephalexin isn't working i feel like i have a rash and its extremely uncomfortable not sure what that is?

? allergy: Stop medication and see your doctor asap. Can use an antihistamine for the rash till seen. Was a urine culture done? If not, it should be.

Two problems: First, you likely have an allergy to "cephalosporins" ( the class of antimicrobials of cefalexin), and should tell your doctors about this. Second, you have likely developed a resistant urinary tract infection, and need to change medications anyway, even without the allergy.