Insomnia Support Group
Insomnia is a symptom, rather than a disease, and is characterized by inadequate quantity or quality of sleep. People with insomnia complain of difficulty falling or staying asleep, which results in significant impairment of daytime functioning. Insomnia is categorized as transient (shorter than one week), short-term (one to three weeks) or chronic (longer than three...

First thing is to relax and know you're going to be OK. As you already know, the anxiety and worry only feeds it and makes it worse.
Have you seen anyone about treating your anxiety and depression. These are likely suspects as the root of your sleeping problems. That means as you treat those underlying conditions, your sleep will tend to improve.
So getting yourself some help will be a good first step, and just the reassurance of knowing you're going to take care of yourself will help you feel a little better, and that will result in better sleep.
A couple of other thoughts for you.
First, you can sleep. At some level I'm sure you know this. In fact, our physiologic requirement for sleep is so strong, so basic, at some point it overwhelms whatever worries or anxiety we may have and we in fact do sleep. Of that you can be sure.
But it's those negative thoughts that aren't true like "I can't sleep" that help fuel and perpetuate the problem.
As far as what to do, there is help. Of that you can be sure. Start with seeing your doc or counselor. If you are the self-help type, you'll also find lots of good info online that is completely drug free to help you sleep better now. Try searching 'cbt adult sleep training' or similar and you'll find much info on that. CBT is the gold standard for treating insomnia and it helps most people.
Be confident there is help, and you will be fine.
Some advice that others have told me is to eat healthy and get some exercise every day, the endorphin release will help nullify some of that anxiety of yours. Also, my CBT councilor recently gave me a technique to try: Give yourself a "worry-time" 5-10 minutes per day. After that moment, tell yourself whenever a negative thought pops up, "Sorry, wait until worry time." Don't blame yourself if you don't perfectly execute it for the first time, for myself I'm still learning how to save my worries until a designated period.
Another method is to use what's called "sleep restriction." It's a bit scary at times, but what you do is have a designated time for going to sleep, and for getting up. Even if you're tired at your wake-up period, get up anyways. This will tell your body that it only gets that time-frame to sleep, and it will adapt to it eventually. Trying this myself, it's starting to work. From the sites I've researched, it's also okay to have some naps, but limit them to 30 minutes if possible, and have them before 3pm.
If you can't sleep at first after 30 minutes or so (some sites recommend 10-20mins), don't just lie there in a panic, get up and do something non-stimulating like reading a book. After about 20 mins, try sleeping again. Sometimes I meditate (meditation can help a lot as well, all you do is sit comfortably and focus for 10-20 mins, if it helps, look up "how to meditate" on youtube).
Also, avoid bright computer or phone screens an hour or more before bed. The blue light coming from these electronics tell your brain it's daytime, and keeps it active while you try to sleep. For computers, there's a program I use called "Flux", and what it does is tints the screen orange in the evening to simulate a sunset.
One more thing (so much advice! Don't worry, I'll wrap it up here soon), Avoid drinking or eating caffeinated foods and beverages before sleep, give yourself up to a few hours at the least for anything with stimulants in them. Anything with carbohydrates and sugar should be consumed a few hours before bed as well.
All in all, just remember that there are people out there who care about you, and will help you should you really need it. Find yourself a good counselor and go from there. You will find peace.