I think if you tell your doctor what you told us, he/she would help you slowly and safely wean off of the Ambien. My doctor was doing just that until I ended up in the ER from an OD. She then immediately stopped prescribing it and I was stuck with nothing.
It's definitely difficult to get off Ambien, but it IS possible! I've been off it since January. The first few weeks were torturous, but after a while sleep came a bit easier and I'm at the point now where I usually sleep 4-6 hours/night most nights. It sucks big hairy b@lls to come off of, but now that I'm a few months down the road, I wake up more easily in the mornings and I feel more awake and alert throughout the day. The few weeks of hell are totally worth it! You CAN make it through and there IS a light at the end of the tunnel, however dim it may seem at times.
Good luck and keep us updated.