hiya, i am 35 and i have the same sort of problem as you ,its only ever my left breast, my underarm hurtsand i get asmall lump appear, i get a feeling that my underarm is bigger and i get pain in my left breast on the far side near underarm, i cant feel any lumps in my breast, but it seems to get slightly bigger at times and i have dishargefrom both near when my period due, keep an eyeon when you get the pains is it leading up to your period write dates down if there is a pattern themits more that likely hormonal,,.... BUT, i would go to a dr for a breast ecam as i did to put your mind at rest.... all the best fiona
From the symptoms that you are describing, the most common event that I can think of would be the result of hormonal stimulation of the breast tissues that coincide with hormone fluctuations during the menstrual cycle. The lump may also be due to fibrocystic disease or fibrocystic changes that is also hormonally mediated.
However, you should watch out for other lump characteristics that may point out to a possible malignancy including irregularity or grittiness in borders, being hard or fixed, or associated with an overlying skin dimple.
You may also require diagnostic tests like mammograms or ultrasound to be definite about the nature of these lumps and breast changes.