Do you do any regular stretching? That could make a bid difference. Stretching can avoid/fix a LOT of problems -

As Anthea said, stretching can solve a lot of problems. Also, many back problems are a result of weak abdominal muscles so have a good ab routine that you do daily could also make a difference.

That being said, if you are really concerned it might make more sense to check with you doctor or chiropractor regarding a chronic pain situation. Some things can be fixed very easily when caught early enough.

Good luck!

Those are my weak points too.
Be very careful to avoid the muscle tissue around the nerve going into spasms. THAT hurts!

I suggest - Ice and heat along with Motrin when you feel it flare. Ice helps the tissue keep from swelling. Heat brings blood flow into the area for healing. Alternate each 20 min on - with a rest between. A friend gave me a few Flexeril (sp?) and I take half when I know its going into spasm. It relaxes the muscle and avoids much pain. Usually happens with yard work and not dance now. Rake the lawn?! ... no way.. not anymore!
Stretch lots! Yoga is great.
Water - water - water ! Banana before shows. Be sure to warm up and cool down even if your show or dance sessions are short.
Check the hip posture and your form. I had to rotate my pelvis under to keep the back unlocked. Its not always in the knees! Get off your toes and root more into the floor from the balls of the feet. Most people who go to the toes with bent knees will compensate balance by tossing the hips a bit more fwd than normal. Go to the ground to take any weight changes in the balls of the feet. Grounded, it keeps the hips solid, keep the hips solid and your back is out of the movement loop. This way, you can be direct center through the core.
Play a whole lot with your postures and a mirror. Find a new happy spot that protects the back! Most will think they are doing it right since that's they way they have done it for years, however, as our bodies change, postures need to be re-evaluated and/or strengthened constantly.
For the hamstrings - Im still trying to figure out what triggers that problem in me. The most obvious has been lacking water on a hot day with a few shows. I try to drink loads but perhaps I dont do enough salt with it. Cant do any of the Athletic drinks due to the sugars, sweetners and other goodies added. They wack me more than anything!
Good luck!

Thank you to everyone who offered advice! I cross-posted this and got some GREAT responses and ideas. :)

Thank you!
~Jeannie

Jeannie,
Very often sciatic pain is due to spinal issues. It could be you tweaked something dancing. I recommend that you having your doctor check it out because, as the above posted mentioned, you don't want to let something serious like a disk go unnoticed. If you catch it early enough you can really make a difference with PT and exercise.

I highly highly recommend, with your Dr's approval, that you look into some Yoga classes. It sounds like your are building some nice strong muscles in your legs, but flexibility as a dancer is extremely important. You will feel much better! :)