Could I Have Fibroadenoma?

I'm 16 and I have a lump in my left breast. It is in the middle, and is painful to touch and it makes my breast feel heavy. Usually i have a dull ache in in as well. Occasionally i have have sharp pains in both of my breasts and the corner of both breast feel a little lumpy. I first noticed the main lump about 20 months ago. I realise i should have gone to the doctors straight away but i am just so scared that perhaps i have breast cancer. Reading about various breast diseases and the types of things that lumps can be, i am not as scared, but i am still very worried. My breasts are often quite warm/hot and feel tender and swollen just before my period. I thought perhaps it could be Fibrocystic Breast Disease or Fibroadenoma, however the lump is virtually immobile and i believe the lumps for these diseases are usually mobile, and for Fibroadenomam, painless. Could it be a harmless breast lump, or is it cancer?

[Cleveland Clinic]

Dear Moonriverandme,  Breast pain is a common breast symptom.  The reason for breast pain is not clearly understood, and is not usually associated with breast cancer.  Breast pain is sometimes associated with hormonal variations and is then called cyclical breast pain.  Noncyclical breast pain does not seem to be linked to hormonal variations and is often localized to one area of the breast tissue.  Noncyclical breast pain may or may not be the result of an injury to the breast.  

Breast cancer would be very unusual in a 16 year old, and perhaps what you are be feeling may be normal breast lumpiness.  However, over the internet without ability to do any further evaluation, including physical examination it is impossible to say for sure what you are feeling.  You may want to have this checked by your doctor who can also review a breast exam with you and discuss your concerns and evaluate further as needed.