Melatonin is a good place to start. I take 5mg sublingual in addition to my other meds.

I am bipolar and have similar sleep problems that you describe. I am now taking meds so my sleep schedule is somewhat better but I still cannot regulate a consistent sleep/wake time and that is very difficult because I sometimes am so sleep deprived I am not alert enough to drive and have had to cancel appts with pdocs and such. I think mine is a manifestation of mania or hypomania.

You should consider prescription meds. Most docs are hesitant to give "sleep" meds such as xanax but the xanax helps me. If you are bipolar though there are other drugs that can help you regulate your sleep. For me bipolar has more to do with changes in energy level than mood swings.