Quoting Ellen Storment:" I used to take melatonin every night before I was pregnant, I loved it! (I never formed a habbit from ... [snip!] ... an hour away from bright lights of TV and instead reading - and if you have to, its safe to occasionally take some benadryl"
Not only those you listed but its also bad during pregnancy because it doesnt give the baby the ability to develop its own melatonin, since its a naturally occurring substance in the body.
OP, I've taken it a few times, never habit forming and I dont get that groggy feeling like I do when I take advil pm or anything like that. I do notice that if I take too much( accidentally took a 10mg pill instead of a 3mg one) I will have bad dreams. My husband has also expressed this to me.