Have you had the sciatica diagnosed by a GP?
Many folks self diagnose and more often than not it is something called Piriformis syndrome. True sciatica is a hot bruning stabbing pain down the back of the leg and does not tend to change 24/7. You should get tot he Doc if this is the case so as they can do further tests.
In general get it diagnosed anyway.. that way you rule out any major problems.
If the pain is a tingling numbing pain in the buttock and down the side of the leg and maybe even into the groin, also if when you move position it at alleviates the pain then it might be prirformis syndrome or a trigger point on the prirformis muscle.
Piriformis syndrome is where this postural muscle in the buttock area becomes too tight. The usual test for this is when you do a straight leg raise and your leg naturally laterally rotates outward instead of the toes remainign pointing upwards, as Piriformis is a lteral hip rotator. PS can also come with a trigger point on the muscle that has a referred pain pattern, see Travel and Simons Myofascial Trigger Points books. Many people self diagnose this pain for sciatica.
Common causes... woman,,, sitting with legs crossed, men.... wallet or ciggies in the back pocket....both cause pelvic imbalance and the muscles have to work harder on one side than the other. Dont forget posture plays a huge part in the buttock area.
If the piriformis muscle is too tight then lying on the floor with a tennis ball in the painful area and waiting till it releases can work... if you have true sciatica....this is not something to try without therapeutic guidance.
Good youga stretches on both sides of the buttock area will help too.....
best wishes