from what I heard melatonin causes horribly vivid dreams though.

also, this may help.
Trauma Nightmares and Lucid Dreaming - Kellevision
(I found that since i can't do lucid dreaming, i just recap the dream, however brutal it sounds and then end it on the note i want it to end. that way I realize it is a dream and can manipulate it to something less scary).

I had interesting experience with salvia (a brew... I used like 7 or so small leaves of the plant)... I had dreams on it, vivid and my mind was going to memory lane.... but I was able to think of it... neutraly (and I dug up memories tht were cool but forgotten). I am not sure I would recommend it though, as it is potent plant and it's said that in salvia daze you will see yourself the way others see you.... (to get really high though, you would need much more of the plant).