Could it be?

Hi all,
I'm currently beside myself and would like your opinion please. I have a strong family history of mnd. My father, grand father, auntie and cousin all died within 9-12wks of diagnosis. Very rapid progression....
The last 2wks I've had lots of twitching in my body and predominantly in my bicep muscle. I can barely lift a shopping bag or pick up my kids with that arm BUT I don't have any other muscle weaknesses or inability to do anything. My neck also feels heavy and different. I can still lift my arm above my head and use it. Is it just early days and it will end up losing all mobility in arm? I lie awake at night with twitching all over my body and dread going to bed. I passed all the tests at the Drs with pushing, pulling etc... Can mnd start like this? is it slow progression with the muscle wasting? All through my neck, shoulder blade and bicep muscle. 
I'm not coping very well. I'm not seeing a neurologist until next week. Thoughts??