Kiran,
The pain you are feeling is quite palpable. You must go to see a qualified Yoga teacher or therapist for an in-person evaluation. [I]This cannot be done here on the forum, regardless of the amount of details that you may eventually offe[/I]r. This therapist must be able to work with your current doctor, or a any doctor you choose who also knows the details of your situation. There are many threads on sciatica here, but you will quite likely cause more harm to yourself than good if you go at them in this current state of suffering. Please begin to hydrate as Mukunda details immediately and also to start the Indra Devi’s diet. It is a supremely beneficial anti-pitta diet, not solely arthritis, that should lessen those aspect of the pain and symptoms that you are experiencing. And please, go get one-on-one help if you would like to also include Yoga in your treatment; whether you have to barter, trade or pay, it is absolutely necessary with this type of early fusing and resulting sciatica.
Kindest wishes for your comfort and relief,