How long does it take for sciatica to heal?

I have this problem for around 5 weeks now and it seems to be getting worse, not better. I work in a call center so pretty much sitting down all day. The first physio i went to said this was the cause. I went to him 3 times but wasnt making a difference. I changed to another physio 3 days ago and since then its really painful on my calf and hamstring which makes it difficult to walk. My doctor prescribed me painkillers with codeine but its still painful sitting or standing. I know it varies between people but was wondering if anyone had/has sciatic problems how long did it last?