Swelling post op

Hi I had a mx on 12th and discharged same day. I now have a seroma which developed the following day. In my opinion it’s huge. Almost the size of my good boob and it’s not getting any smaller. My doc and bcn told me this might happen but I didn’t realise to what extent. I haven’t had a drain and both are reluctant to do this as it isn’t causing any pain and have said the drain may cause infection. My underarm is quite sore though. I also had sentinel mode removal for biopsy. Im still doing the exercises. The doc and bcn are not concerned but advised to make contact if the area seems red or feels hot. Has anyone had the same experience? How long does this last before re-absorbing ? I have my post op appointment after Christmas. Are there any questions I should be asking? Grateful for any advice. Perhaps I’m just being over anxious!