If you have a natural health food store nearby, ask for a brand of magnesium called Natural Calm, and also a good quality calcium supplement. They both help to relax you. Take before bed. You can also try GNC for the supplements- they are better quality than grocery store products. Take a warm bath and drink 1/2 cup whole warm milk before bed as well. Reading a magazine until you are drowsy helps also. It sounds like you have anxiety induced insomnia, and believe it or not, you can work yourself out of the insomnia. Every night before bed, make sure you have a calming ritual that relaxes you, and eventually you'll start sleeping better. I've tried valerian and melatonin, and they don't work for me, but everyone is different. Ambien might work- call your doctor, but try the natural route first.
I have the same issue before we go to Aruba- I think I worry that I'll oversleep and miss the plane, so I completely relate to your situation!
Good luck and enjoy!