You sure its a Sciatica? Is there radiating pain down your the outside of your leg, even to your feet. Does your leg go numb? Because a sciatica is a nerve, and pressure on the nerve causes it to shoot pain down the leg and even numb it in some cases.
If its the Sciatica its tough to call whats causing it. Because the Sciatic nerve has a few points were pressure can be put on it. One is in glut muscle, if that is week it can put pressure on the sciatica. Another is in the base of the spine, were the nerve reaches the spinal cord. If thats the case, you could have a bulging disk in the back.
I would go see a doctor and get a scan done on your back to make sure its not a herniated disk. Because if is, then you will probably need physical therapy. If not, then you probably can just start doing light exercises to build up muslce strength around the area to take the pressure off the nerve. Also anti-inflamitory drugs can take the pressure off the nerve.
I had the issue were my glut meets my back, thats my week point. It happened after i slept on the couch, bad idea. So for about 3 months i slept on my bed with my feet elevated. I would fold a few blankets ontop of each other so i can sleep on my back. This position with the knees up takes pressure off the back in that area. I also would massage the area with a tennis ball, just lay on it and roll it around the area, its a great massager. I would also constantly ice the area and take advil. That and i continued with my weekly working out, i would jog, and do exercises in that area, i made sure i warmed up first before hand. It took me about 3-4 months but i have little or no pain now.
After that i started big time on doing exercises to get my hip flexors and abductors, as well as my gluts strengthened.