This is the brand I buy on Amazon. It may be too high for you but they probably have lower doses as well. I'd try 5mg, or if you buy the one I referenced, cut in half = 6mg. They are very soft and likely to crumble so I'd see if they have other (lower) doses.
It does the same for me, and I've taught myself how to have lucid dreams which really become fun. I usually have 3-4 lucid dreams a month. I also take Huperzine A to promote dreaming, and find that I'm much more refreshed in the morning after a night of good dream activity.
One thing to mention, I don't think it is possible to OD on melatonin. I've read studies where massive doses are given at night to patients on chemotherapy, and melatonin as an adjunct is shown to improve outcomes in a statistically significant manner.
I've found this brand on Amazon to be quite good. They are chewable and have a nice taste. You can try taking 3-4 of them and see if that helps your insomnia. Most people can safely take 4 without waking up feeling groggy. I saw one study where they were looking at a range of doses for adjunct cancer therapy and the top dose was 600mg, and that group's side effects was mostly limited to morning grogginess.
I've also forgotten mine when I've gone out of town and had to miss several nights. The only thing that happened was I didn't sleep well.