I Have Been To An ENT Doc And Had A

I have been to an ENT doc and had a brain MRI with no obvious answers for my symptoms(NO stroke or mass)....I lift things as much as 50 lbs. at a time at work...after 4 or 5 hours , I have an incredibly hard time keeping my head upright. It feels like I am trying to lift a bowling ball with my neck. Total weakness and is easier to walk with my head facing down! Very difficult to raise it up, sometimes use my hand to push upright.
This is after my original symptoms of occasional slurred speech, which started about a month ago. I have a Nerology appt. scheduled for March 8. Any ideas what it might be???? MS or ALS???? YYYY@YYYY