Hi Anika,
I would definitely try the lemon balm, can't hurt. Also there is an app called Deep Relax DM. Some days it helps and other days I find the guy's accent to be a bit annoying. Its free though and since you can't sleep anyway it can't hurt. I know you said that meditation wasn't really helping but worth a try. Sometimes I have a hard time meditating on my own so the guided thing kind of works for me.
A few other tips that may or may not work; I have only been sleeping because of starting the seroquel this week so obviously not the authority but maybe try: eating some complex carbs before bed-sometimes it will boost your tryptophan levels, the lavender is always a good idea- I have a lavender lotion that i actually put under my nose

, I know you said the melatonin makes you weird but I wonder if perhaps it may be that it is synthetic? Don't know...But- I recently bought montmorency tart cherry juice (the one I got was concentrated), I take two tablespoons before bed. It has a buttload of melatonin in it. It tastes good, too. Just a thought.
I hope you get to feeling better. Sending positive vibes your way.