Pain behind breast

I am a 28yr. old female.  In Jan. 2007, I found a lump in my right breast.  After about 2 weeks it was gone.  Since that time I have had pain behind the right breast.  At first the pain would come and go, now it is almost a constant.  The pain will radiate up into my collar bone area and down my right arm.  I will have "bad" weeks where I am very tired and not much energy along with the pain.  I went to the doc Oct. 2007.  I've had a breast ultrasound and bloodwork and all seems fine.  This month I went for a chest-xray and am scheduled for a CAT Scan.  In the meantime I am worried and wondering what this could be.  I am wondering if the lump I found was just a coincedence, since the pain seems to be inside, behind my breast.  It is very hard to describe the pain, but it is not like a pulled muscle or anything.  Any input would be helpful.  Thanks!  

[Cleveland Clinic]

Dear Brit28:  Breast pain is quite common, particularly around the time of one’s menstrual cycle.  Breast cancer is not usually painful.  As you describe the pain as being behind the breast, it may or may not be related to the breast tissue.  Without evaluation, it is impossible for us to speculate on what this might be.  Hopefully the CT scan and Chest x-ray will shed some light on this for you.  

[Brit28]

Still no answer!!

[Weoble]

I had a noticeable lump under my right breast and several under both armpits. My grandmother had two mysectomy's and I was worried. I went to dr. Had a mammogram and they said I had to have an ultra sound. They only did an ultra sound on one part of only one breast. It came back negative. Both breast still have lumps and under both arms are very sore both with lumps. Should I go to another dr. And start over. I'm 38 and really concerned. I have inverted nipples with
some leakage and explained this to dr. Please help me understand. Could this be cancer?