Listen to your doctor. If you don't trust him go and see a neuromuscular specialist at a ALS certified clinic. Get an EMG and a MRI. If your reflexes are normal then I highly doubt it's anything life threatening. But I'm not a doctor. I been twitching for 5 years, and have been where you are mentally. Get a second opinion. Tell the doctor you want an emg.
Did you get an MRI, EMG, it sounds like benign Faciculation syndrome but you should see a neuromuscular specialist, have an emg and a physical exam to put your fears at ease. Doesn't sound like ALS but I'm not a doctor.