Painful breast lump

I am 21 years old, and for the past 2 months i have had this painful lump under my breast, i went and saw a PA about it and she said that it doesn't feel like it a cancer lump and that's all she did.  I have noticed that it increases and decreases in size and it only hurts when i press on it.  You can't really see it at all but you can definetly feel it right underneath my right breast, i would say it's about 1/2 in long.  Do you have any recomendations?

[Cleveland Clinic]

Dear army_combatmedic:  There are many possible explanations for painful lumps.  The most common is related to menstrual cycle and may explain why it gets bigger and smaller.  Most breast cancer is not painful.  Breast cancer is also uncommon in women in their 20’s.  If you remain concerned you could consider a second opinion.