Hi!
I am sorry to hear about your medical problems. ALS can be confirmed or ruled out only after a detailed neurological examination showing signs of both upper (muscle weakness, decreased motor control, inability to perform fine movements, increased spinal reflexes, and positive Babinski sign—great toe going up) and lower motor (muscle weakness, abnormal EMG etc) neuron weakness in at least one limb.
Apart from disc problems in the back and anxiety and panic attacks, muscle spasms can be due to several causes. Dehydration and electrolyte imbalance, muscle fatigue due to overuse, pinched nerve due to wrong posture could be the cause in your case. Try and use the correct posture while sitting and walking and consult a physical therapist regarding some stretch exercises which you can perform to help relieve tension.
If this does not help, then I would suggest you get the blood levels of the following checked if they have not already been checked: potassium, calcium, sodium, magnesium, vitamin B complex, or vitamins B1, B3, or B6 and Vitamin D. Generally deficiencies of any of the above can cause muscle twitching and spasms in localized or generalized areas of the body. Get your kidney function, parathyroid gland function and adrenal function tests done because these affect the electrolyte balance in the body. Stress, alcohol, caffeine and fatigue all cause similar symptoms. Hence if you take alcohol or coffee then cut this down. Sleep at regular hours and see if it helps. Certain sleep disorders and peripheral nerve disorders due to diabetes, Lyme's, lupus or hypothyroidism can also be the cause. It can be benign fasciculation syndrome if all causes are ruled out.
A comprehensive investigation is required keeping all the points in mind. Please consult your doctor regarding this. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.
In case it is helpful to know, I am a male in my mid-twenties