Honestly, I'd check w/the doctor who prescribed it for you. The right dose should help you sleep easier because it calms your mind and allows your tired body to do what it needs to do without interference from your brain.
Depending on what you're taking with it, that is. My combo is Cymbalta/Depakote. The doctor hasn't yet prescribed Abilify (I've taken it before), because I'm currently using something else to control anxiety. I'd check with the doctor first, even before choosing herbal remedies, like melatonin.
:-) Good luck!