Lymphodoema during RT

Has anyone had experience of developing lymphodoema during RT? I have had 5 of 15 sessions. I got home from the 5th and noticed my arm was swollen. Typical it was on Friday before bank hol weekend. I phoned the emergency number and was told to observe and seek help if it gets red etc etc. It’s not red, hot or inflamed at all. I’m keeping it elevated and doing the hand and arm exercises on the cancer research uk website. I’ve been told not to do anything that will alter the shape of my chest cos they use that to line up for RT. My immediate aim is to stop it getting worse and I’m winning so far. I paint and I cannot afford to have a swollen hand. It’s what is keeping me sane throughout this ride of hell. They are surprised it has happened this early, during my RT. I think it might be an hot car journey to the appt or maybe a tiny insect bite on my neck. It isn’t unusually red or inflamed. Anyone else had this during RT? Will I be able to continue my treatment? Thanks for any help.