What to use on a rash just above... my butt crack😖

OK so I never really take the time to cut and remove the tags sewed at the back of my undies and it never occured to me that it could cause such an unpleasant rash. Now it itches like crazy and being 39 weeks pregnant with all the VD and everything I cant exactly go commando style. I tried to put on lotion but it creates humidity and actually makes it worse! What can I do to stop the madness!!!!