Fixing my sleep schedule

For the past few weeks, I've basically been nocturnal. I just can't seem to fall asleep at night, but when I do sleep, it's from about 5am-Noon. I normally work from 4-11pm. My huge need to fix my sleep schedule is because I have to go to a work event in two weeks and it requires me getting up at 7am and I'm scared that I won't be able to fall asleep the night before. I already take melatonin supplement but I think I need to move onto something stronger.