Suggest Remedy For Painful Sore Bumps On Outside Of Vagina

Have painful to touch sore/bumps on outside of one lip of vagina. Never had this before and family doc has never seen this before. What could this be? No sex in months...since husband had hip replacement and he's been my only partner for life.
Doc put me on sulfameth/trimethoprim 800 twice daily for 7 days. I'm on day 3...painful to touch and doesn't seem to be going away. I am 58 yr. Have been on Premarin, but also just began weening myself off...had complete hysterectomy 14 yrs ago....pre cancerous cells.