Two things: I've heard from some that melatonin shouldn't be taken with seizure meds. From what I can see, there's no conclusion one way or the other but something for you to look more into maybe?
Secondly, a bunch of us were having this discussion the other day. Apparently, a bunch of moms have seen an increase in mood swings and bad behaviors in their children who take Keppra (levetericitam). You may want to have this discussion as well and try another medication.