Rash on chest

I'm currently 4 months pregnant and have had a rash on my chest fit about 3 days now! I don't think it's from any lotions or oils as it is the only place I've broke out. I still have stopped putting anything on it just in case. I did start putting Benadryl ointment on it and it seems to be finally getting better. It is peeling like crazy though! Happen to anyone else? Any recommendations?