Severe Siatic pain

Have been suffering with pain from hip down left leg to foot for around four months, cannot sit for long, cannot stand for long Have been put on a brisk walking programme and gentle cycling in a pool, but still the pain keeps on coming back.
Would love to know the best way to try and relax to escape pain for even just a few hours.
I am told I will soon be able to have an epidural – but how long will this last.Any help appreciated – I take a cocktail of Paracetamol Co-codamol and even diazapan when the pain drives me to. Obviously not a good way forward but you get desperate with the pain.