I just found out I have sciatica and herniated disc, but I want to get pregnant. Is it possible?

Yes its possible. You need to discuss with your OB/Gyn on how to deal with the sciatica while your are pregnant. If you can I would get the sciatica under control first before getting pregnant as the rigors on the body will be better tolerated.
Yes. but recommend getting the herniated disc and the sciatica treated first. The discuss with your OB and an orthopedic surgeon before trying to get pregnant.
Get surgery first. Pregnancy is a difficult time to carry a lumbar disc herniation that is causing radiating severe leg pain. Surgery can be done toward end of pregnancy if needed but it is a hard wait. If you have tried 6 weeks of physical therapy, epidural steroid injections and rest but leg symptoms persist then get the microdiscectomy done. You will be happier while you are pregnant not worrying about leg pain.
Yes/no. It depends on the level of pain you have and if surgery is needed to treat the disc. Consult you orthopedic doctor before pregnancy he/she will advise you on when it is safe to concieve.