Hello DOUBLE. There are many reasons for the Boil. Changing detergents, diets or having a weakened immune system can all cause this problem, but since you were sexually active I would tell the Dr to make sure everything is okay with the boil. Having a boil does not necessarily that it is an STD but I would still have it checked to make sure. It is better to be safe than sorry in this case. Take care Double. I hope things go well with your Dr Appointment when you go next week. Soidhonia