I Have A Rash On The Upper Half Over My

I have a rash on the upper half over my thigh and lower half of my butt cheek. It sometimes burns or itches and when using lotion it burns. I was told i had a small risk at getting sjs from my medicine could that be what i have? I have been on lamictal for two year amd this the first time it should (3 months ago ) but we also switched to a new laundruy detegent and it is changing from summer to fall. Should i go to doctor or urgent care? What should i do to help it go,away?