Deborah, I hope things are going well. I have gained weight as well. I have been a gym trainer earlier in life, so I feel, like many others probably. how important exercise, movement and flexibility is. I did not try any of the weight medications though I must admit I have hesitated from taking prescribed amotripyline 10mg ( pain management) after I stopped gabapentin which caused me a lot of gain. Amotrypline may also cause weight gain, so I hesitate, despite the fact I am less mobile. I notice you are in the Uk (as I am).
I would reccomend you try neurohereos https://www.neuroheroes.co.uk/. They do classes for all types of neurological conditions and depending on your personal situation you can get access to the community exercise fund via a GP referral to them. They have experience with MG patient (me). The classes are for seated, standing or a little more mobile patients and the teachers are trained movement teacher and physios. Once you complete your initial assessment, you could mention you goals, and be sure to keep your GP or neurologist in the loop with any medication changes are the providers of the weight medications may well not be aware of neurological conditions, so you'll need to be on top of your admin, or your carer, relative, supporter will need to add the medication changes to your personal plan. incorporate regular movement classes in your schedule to aid your digestion,daily flexibility while managing your condition under your medical professionals. See a loss of pounds as a happy side effect of overall well being and increased movement, where possible, according to your condition.

Online Parkinson’s & MS Exercise Classes | Neuro Heroes

https://www.neuroheroes.co.uk/