First of all Amitryptiline is a mild anti-depressant that can help you sleep, but will not reduce pain. It is not a pain reliever at all. I suspect you were given it because you were showing signs of depression due to your pain. You should have been given a prescription for anti inflammatories, and real pain medication. Also your doctor should have sent you to a physical therapist. Next time you see your doc I would bring this up to him. I had a herniated disk a few years ago, so I know what you are going through. After you get the pain under controll you will need to do daily strengthening excersises to tighten those back muscles up. Your physical therapist will show you. Make sure you do them, it is very important.
Good luck to you, it is a long painfull process but you will get better with proper treatment.
Gracie