Ouch. Be sure you aren't making the situation worse by trying to feel better. Only your physical therapist or physiatrist can advise you truly.

When in proper posture, each vertebrae sits on the next and can withstand huge amounts of weight. It's when something isn't working right that we experience pain etc.
http://healthguide.howstuffworks.com...a-in-depth.htm

Sitting upon a pillow can easily cause more problems. A lumbar roll is generally what helps the problem, even though it hurts more or is uncomfortable to begin with.

Try taking a stiff ice pack to sit against at church. And the lumbar pillow.

Keeping the stomach muscles toned is key to increased strength in the back, and to keeping bones in place. Talk about tough! Also, for sciatica, keeping the hamstrings stretched is paramount for minimal pain. (The sciatic nerves are nearly the size of your thumb, around, in places and are really deep within the structure.

Use meditation and relaxation exercises to calm and de-stress. Muscle tension creates added pain no one wants.

Be careful with too soft a bed. It can exacerbate some problems. The feather/down comforters need to be covered with one of those fancy microbial covers. The price of having a down comforter cleaned is often as much as the purchase price, I've found. (Can't have down, can you imagine how long that would last with a retriever dog? )

Try a TENS unit...there are charts to help you with placement of the electrodes to circumvent your pain of the day.

Everyone is different, as I said, but my PT says the more "movement in pain" in trying to escape it makes things worse. Make sure your movement is therapeutic.