Similar problems here; it's what helped me believe I have bipolar instead of "just" anxiety and depression. (That and obsessions that almost completely go away when I take lamotrigine/Lamictal. )

What I do when untreated is to sleep well one night, and then the second night, not a minute of sleep. All the sleep hygiene in the world does nothing. Sometimes I'm not sleepy at all, other times I'm tired but just can't sleep. After that extemely long night and the following extremely horrid day, I sleep well. Next night, zero again.

My research into this weird pattern said that it was a sign of bipolar. (I had already had the diagnosis, after about 10 years of wandering around trying everything. I just didn't believe it.. I thought I had never been hypomanic, but now I've thought of some things that might have been. Another story.)

I tried Ambien in the past and it sure did knock me out but it has drawbacks for me. Remeron/mirtazapine was and is better for me. It's most effective at first (and, they say, at a low dose) but it still has a mild sedative effect when it's lost the knockout effect.