Hi Tetley and welcome to the forum.
Your post implies that you have kappa light chain myeloma. If so, do you know what your lambda light chains are? The kappa/lambda ratio is also relevant, as a ratio in the normal range may indicate that both are high, maybe due to a routine (but possibly symptonless) infection.
Do you have any information on what the possible treatment change might be? I recommend really pestering them with questions (or if you are uncomfortable with doing so, going with a friend or relative who does that).
The frequent changes of doctor is also bad because there is no chance to build up a rapport.
I also suggest asking for a paper copy of your blood test results. You may also be able to get test results on the NHS app.
By the sound of your post, you have got to take control of the situation.
All the best.
Regards
Rabbit