There are some tests that can be done. Your doctor can examine your movements, check your reflexes, and assess your pain pattern. Questions about what you can and can't do in the way of movement and activities also give helpful information.
It's generally accepted that if a patient feels better and can do more, it's a good sign that healing is taking place. You can trust your sense that you are getting better. Many people make the mistake of sliding back to their old ways once they feel better. It's likely they will have a relapse.
Weight loss and exercise help prevent and cure many conditions. Keep up the good work.