I used to get acne around my mouth pretty badly (really inflammed, painful spots) and I always believed that it was due to horomones. I've heard various times that recurring acne near/around the mouth and most lower half of the face usually means that it's due to horomones. The reason I don't have most of it anymore (though I still do break out occasionally "near" my mouth/chin) is more than likely because I went through two courses of Accutane, and after my second course I don't wear anymore makeup. I always felt like makeup erraticated (sp?) the problem.
I would suggest going to your derm and talking about birth control maybe? That usually clears women up if it's due to your horomones.