HI,Dear, Thanks for the query from you for your painful ,swollen pea sized bump every mthly ovualtion,which hurts with pressure in outer labia, which goes away in next 2-3 days time.1-I am happy that you are serious to know why this painful outer labial swelling comes and goes with each of the mthly ovualtion cycle.?2-In my opinion this painful swollen in outer labia is bartholinian cyst,which gets mildly infected and swollen with increased secretary activity in the Bartholins cyst with ovualtory changes in the cyst walls, which resolves as the cyst discharges with overflowing cyst fluid secreted during the mthly ovulatory cycles.3-AS such this painful swollen bump is the ovulatory bartholin cystic overflowing activity,which is being felt by the patient, having active sex life.3-In my opinion-possibility of mild infection with active sex life would explain the recurring bump every mthly ovulatory cycle.4-I would advise ER-Gynaec opinion and chekup and would advise -excision of the bartholins cyst under antibiotic cover if, it is disturbing the active sexual life of the patient much.5-Hope this would resolve the causative worry of the patient in question .6-If treated on this line, the fearing patient , should not worry you much.7-Hope this would solve your worry of the painful louter labial bartholin cyst lump every mth,with the ovulatory cycle.8-So urgtly take -the advise from the ER Gyanec Surgeon.9-Wellcome to HCM for any more query.