Could lump in breast be milk duct?

[majors3]

Ever since I started breastfeeding my DD 3 years ago, I have had a very small lump in my right breast. I would notice it was there more when my breasts were full and couldn't seem to find it when they were empty. After I had been nursing for awhile it seemed to dissapear. Then, when I got pregnant with my DS last February I notice it again, the size of a nickel maybe. I asked my midwifes and they thought since my breasts are kind of lumpy anyways and it seemed to some and go with Aurora that it was probably just a milk duct. Since DS was born I honestly have not paid any attention to it. . . until 2 nights ago when I rolled over in bed on to my back, put my hand on my chest at felt a Huge lump. Like the size of a small egg! We are just switching insurance and it isn't effective till October first otherwise I would go right now! I am still hoping it is just a milk duct backed up. And that it might have something to do with my hormones since I just got my period back. And it does seem to get smaller when I am nursing often? Anybody have any experience with this? I have no other symptoms except if I keep pressing on it it does feel a little tender.