I stopped using Melatonin for a while because my bad dreams were amplified. I used Skullcap herbal tincture and that worked okay, although I did have a bad dream with it. When the bottle ran out, I bought Valerian tincture, just around a week ago. I have to say I had one disturbing dream on it, but I can't really blame it all on that herb.
I've found that even when I take a half of a Unisom capsule, which is just an antihistamine that makes you sleepy, I can have a series of nights where dreams are not a problem, but then I will have one upsetting dream. Honestly, even when I take no sleep supplements or meds, there are times we all seem to have 'nightmares' or bad dreams.
Dreams are just an outlet, if we have a bad one it's probably a sign that something is disturbing us in our everyday life or sub-conscience. It's nature's way of giving us an outlet of our fears and worries, and we should accept them more readily rather than try to escape them completely. Some people don't dream at all, or never remember their dreams, and that, in my opinion, is worse than having a bad dream.