Underarm lump while breastfeeding...not going away

About a month ago I noticed a lump between my right breast and underarm.  It was painful at the time, but the pain went away after a couple days.  It is still a little tender to the touch.  I had an ultrasound and they couldn't determine what it was...just that it was not a cyst or a lymph node or anything with fluid.  Speculated that it might just be a milk duct.  I've been breastfeeding for 8 months, and am wondering if it is a clogged milk duct, is that normal for it to last for a month without ever getting infected?  And should I think about stopping breastfeeding to see if that makes it go away?

[CCF-RN,MSN-rf]

Dear mojo29:  Without reviewing the ultrasound, it is impossible for us to comment what this could be.  From the information you have been given, it sounds as though it did not appear suspicious to the radiologist.  However, if you are concerned, you might address this with your doctor, or alternatively, with a breast specialist.  Most breast specialists are located at large academic teaching facilities.