I had some sleep issues (nightmares in my case) as well my therapist suggested I keep a dream journal, I always have had vivid dreams so I don't know what causes them the best I can suggest is work out in some free time and it will exhaust your body to sleep better.
I recall having sleep problems as I wrestled with all the gender issues back in transition. I still have sleep problems but for different reasons these days. I find that if I take a Melatonin (a natural compound found in the market's vitamin section) that I am usually able to fall asleep and stay asleep.