I had a lumpectomy on 9/21 for DCIS. My breast also got very firm, huge & developed a Seroma. My breast sounded like a half full milk jug, with the built up fluid making sloshing noises every time I moved. The Seroma will eventually reabsorb in your tissues BUT if it’s becoming painful with the swelling that accompanies the fluid your surgeon can drain it. They don’t like to do this since it can lead to an infection. I had my surgeon drain it on my post op visit. It did return but it wasn’t as much fluid & it seems to be going away now. From my research this happens 30% of the time after a lumpectomy so it’s “normal”. I found it helpful to keep icing every 30 min on/off for the first 3 days. The ice felt wonderful! I also wore a very supportive/compression type bra 24/7 for the 1st month. I hope this helps & you start feeling better over the next few days. Try not to take any type of pain reliever that would cause blood thinning which will add to the problem.