It does sound like you’ve been pretty much abandoned by the health professionals.
Carole is quite right, a GP is not the person to diagnose MS, it’s a neurologists job. Plus, whether you’ve been given incorrect information, or just not understood what you’ve been told, it seems like you’ve been left floundering with no idea of what is going on with your body.
Basically, demyelination is the process by which nerves are attacked by our own immune system. The immune cells attack the myelin which covers and is supposed to protect the nerves. When the myelin is attacked, it causes relapses, or symptoms of that demyelinating attack. What happens after the attack dissipates is that often lesions (aka scars), are left behind on the brain or spine which may or may not leave ongoing damage causing symptoms even after the relapse goes into remission.
Demyelination is not a primary stage of MS, it is part of MS. If you are experiencing relapses, then you don’t have a single episode of MS like activity (what is known as a Clinically Isolated Syndrome or CIS), you actually have MS. Which is what it sounds like you’ve been told by your GP. Without any further guidance.
The symptoms you describe sound all rather typical of MS, either you have a relapse which gives you new or repeated symptoms, or nerve damage from prior relapses which causes ongoing symptoms (things like fatigue, poor memory, pins and needles and/or spasms that are always with you).
I think you need to see a neurologist and see if you can be prescribed a disease modifying drug (DMD) to prevent further relapses. The neurologist may want to do another MRI, but either with or without a new MRI, should be able to confirm that you do in fact have MS, not a one off event. As Carole said, you might have to be re-referred to the neurologist, or you may not. It depends on whether you were discharged by the neurologist you saw initially.
As far as not being able to contact an MS nurse, that’s pretty terrible. I would expect that you’d have regular contact / appointments with an MS nurse. That nurse should be able to tell you all of this and maybe can get you an appointment with the neurologist if you’ve not been discharged. If you were to keep trying to contact the local MS nurse, you might find you can access more support from him/her.
Both Sarah and Carole are right in that exercise can help. Gentle exercise (at first, especially) can help with symptoms and your mood too. If you’ve not seen a physiotherapist, perhaps you could be referred by your MS nurse, neurologist or GP. And if there is a local branch of the MS society, they may be able to help with exercise sessions.
If you were to hit the Get Involved box at the head of this page, then scroll down to ‘Find Support Near Me’, you can type in your town or postcode and see what is going on in your local area, from exercise to social events. This could help with your loneliness.
Best of luck.