I am experiencing a dull pain in my left breast. The pain is dull, but is worse when I press on it. The pain feels to be behind my nipple or to the left side. I am 26, no children. It has been like this for a couple of weeks. I had a regular menstrual cycle, although due to missing a few birth control pills, my period was longer that ususal. I have been feeling this pain for about a month. I rotate my bras regularly, and have not had any new ones recently that would seem to be causing the discomfort.