We had a party for our son this past Sunday, so I didn't pump or nursed him for 6 hours on the left breast. When I'm at work, I usually go 5-6 hours before pumping too, so it shouldn't be that unusual. So Sunday night, I felt pain on the left side of the left breast. I nursed him mostly on that breast that night and Monday night is when I noticed a big tender ball when I'm turned to the left side (nursing him) and cupping the breast around that area, I can feel a ball like lump. It is painful when squeezed. I've massaged it towards the nipple area and continue to do so when nursing him, it's still there.

To further describe, I would hold the breast starting in the inner part of the breast and with my thumb and index/middle finger on opposite sides, gently swirl around.
I know plugged ducts can feel vastly different occurring at different times and different to each women. Does what I'm describing sound like a plugged duct? how do we determine a plugged duct from a breast cancer lump?
During the early weeks of nursing, I've experienced engorgement and some plugged ducts but it didn't feel like this one. It's usually on one side, this one as mentioned above thumb and index finger on opposite side, squeeze it together I can feel a round lump. I'll give it 2 more days...before totally freaking out and going to get it checked out.