My two year old refuses to sleep i've tried everything. is it safe to give him melatonin? he's exhausted crying and i don't know what to do?

There is no reliable research data on melatonin use in young kids. I would not. Consider looking into Dr. Ferber's method of teaching the kid to self soothe & put themselves to sleep. First accept you are not in control. It is okay to invest in noise cancelling earphones when you have done all you can and take a good relaxing soak when exhausted. With Ferber's techniques you may get your life back