Elloo - I'm sorry to hear you're so worried and that cancer runs in your family.  The lump you have found could literally be anything.  Does the lump change or come and go with your period?  It's possible it could be just a cyst due to hormonal changes - as I'm sure your near that age.  My suggestion would be to talk to your mom or aunt or anyone you feel comforatable with.  Anytime something like this if found it's best to bring it to the attention of an adult and a doctor and have it checked out.  It's always better to be safe than sorry.  It's likely nothing as like 85% of lumps found are benign (non-cancerous) but in any case it's always good to get them checked out so you can put your mind at ease.  I'm glad that you are so proactive when it comes to your breasts.  Keep up the good work!

Best of luck to you!

Angi