Hello All, worried here

Hello

Im 37 and currently breastfeeding my 3rd child. With my 2nd child I noticed a lump in my right breast, kinda at the top, it's about 1.5 cm and hard, doesn't move. It was very prominent when my breast were full, I had it looked at and the Dr said oh it's a plugged duct. After that, well never worried again. Well 2.5 years later the exact same spot is there. I have a hard time believing a plugged milk duct would stay around 2.5 years wo causing infection. I also have a large hard tender lump in my right breast on the right side. My nipple has changed alot on my right side, it kinda inverted? My 3rd child can't latch without a shield, others no problems latching. I started having severe joint pain last week, went to the Dr today, she didn't seem worried about my lumps. I tested positive for strep throat, but no fever and my sore throat only started 2 days ago, pain started over a week ago in my joints. She tested everything, thyriod etc all came back normal except my liver enzymes were elevated and I had a high ESR rate of 90 validating my joint pain. I guess normal is 20ish. Upon research I see the high levels could also be an indicator for BC. Im very anxious to see my regular Dr. On the 20th at my 6 wk checkup. However I was told a mammogram wouldn't be good for a lactating breast, but ultrasound would be. Is one better than the other? Thank you for any advice and for sharing your stories.