Ahh, I understand your pain! I had scaitic nerve pain last week, and it was awful. I called the physical therapist who had worked with me recently after my foot surgery, and he made some suggestions that really helped. First, he said inactivity (like sitting for a long period) will just make it worse. You need to get up---no matter how painful it is---and keep moving. Walk around as much as you can.
He said to use ice, NOT heat, since it is a nerve that's affected, not muscle. (Duh! I had been using a heating pad! No wonder the heated seat in my car made it feel worse.)
Also, he gave me an exercise to do, which I had actually done several years ago when seeing a physical therapist for back pain. I did it before bedtime, and voila, the next morning, I was amazed that the pain in my buttock, leg and calf was gone!!!
I'm not sure you can do this pregnant but if you can, it sure works. Lie on your stomach on the bed. Put your hands down on the bed under you, like you are going to do a push-up. Elbows out at your sides....Then do a push up! Slowly push up while inhaling. Get all the way up on your hands, extending your arms straight (if you can). If the nerve is too inflammed, you might only be able to go up part of the way. If so, that's ok. Just go up as high as you can. Arch your back. Hold the pose about 10 seconds. Then slowly exhale as you lower your arms and go back down to the bed.
Repeat several times.
Although it may hurt your lower back when you're doing this, this motion really helps relieve that sciatic nerve.
I hope you can understand my instructions. Good luck! I swear it works! The therapist told me to do these exercises anytime after I vacuum, mop the floor, or do a lot of bending over during the day.
It's working for me!