I suggest you to try that weird but super-relaxing thing called ASMR.
Just search a bit on Youtube, choose a pair of videos that work for you, wear your headphones and lay on bed.. zZZzZzz

Yeah, this works for many people. Even if you're not "triggered" properly by any type of sounds, the voice alone is calm and soothing enough to make you sleepy.

If you're insufficiently tired I recommend having children.

My problem is I am a night person stuck in a day job. But what works for me is to turn off the TV and any electronics that use LCD's off at least an hour before I want to sleep. I clean dishes and read my kindle for the next hour or so and usually after that hour I am ready for sleep. I also stopped drinking caffeinated beverages over a year ago, and my allergy meds help with drowsiness. I also try not to think about what I have to do the next day when I hit the pillow.

There have been a few threads on this, here's my take on it.

I've had sleeping problems all my life. I encounter people that don't understand it, and they ask me questions like "So when you lie down to go to sleep, how come you don't sleep?" as though I'm doing it wrong. Perhaps I am, however most people seem to genuinely be confused by the concept of a tired person being unable to sleep. I envy them. This does mean that you'll get a lot of people trivialising the issue, unaware of how maddening long term insomnia can be.

As others have said, avoid the temptation to treat it with alcohol, not only is this a sure fire route to alcoholism, but also you will then find it even harder to sleep without drinking.

There have been some mentions of melatonin, personally I found it did absolutely nothing for me, but you could give it a go. Once again, you need to avoid becoming dependent on it, you should view it as a short term method to help you develop a regular sleep pattern. If you do find it doesn't work, don't try exceeding the recommended dose, take it from me, if it's not working, more will not make it work, it will just make you ill.

There are general tips for making sure your body is aware that it should be sleeping, I've never had much luck with them, but then maybe I'd be worse off otherwise. Firstly don't use your bed for anything other than sleeping. Don't lie in bed reading a book, or just recline on your bed to chill out. Your body and mind need to associate bed with sleep as strongly as possible. Secondly, make sure you're going to bed at the same time every day, and getting up at the same time every day (people forget that second part). No more weekend lie-ins, you must have a very consistent schedule so that your body knows it's time to sleep. Thirdly, try to cut out all ambient light from the room, I use a face mask to ensure that I don't get disturbed by cars driving by with lights on, or any other light pollution (if you get one of those, get a nice comfy one, not some cheap one from a chemist). I don't know if there's a US equivalent of this site, but I tend to get all sleeping accessories from SnoreStore.co.uk.

Strangely enough, the thing I found helped me most when I was a child, was an audio book of sherlock holmes short stories. I liked the content, but because it was quite smooth, and calmly delivered I found it tended to help me nod off. Unfortunately then half an hour later I'd be disturbed by the tape reaching then end and the button clicking off with a bug thud, but I don't think moden radios would have that problem. You could also try and get hold of a recording of the UK shipping forecast, it's very soporific.

Great tips in the post above. One more tip that helps me during my rare bouts of insomnia: remove any clocks that might be visible from the bed in the dark, like those LCD alarm clocks. I find that, if I see what time it is, I'll get frustrated by the lower-than-optimal number of hours of sleep I'll be getting, which only makes it more difficult for me to fall asleep. The more time passes, the more frustrated you'll get. Without the clock you'll be able to convince yourself that time passes much slower than you think and that it's still only midnight, and so there's still plenty of time for a good rest.

so very true

There's some truly excellent advice in this thread so I won't reiterate it except "Develop good sleep hygiene".

However, I have not see anyone mention Cognitive Behavioral Therapy. Though you made mention of a nurse giving you some exercises - not sure if these were behavioral or physical - please consider asking your doctor to recommend/refer you to a therapist that specializes in treating social anxiety with behavioral methods. Keep in mind that we all learn to do some fairly amazing stuff (like reading!) and the human brain is literally designed to learn new things, so learning new modes of behaving in social situations is truly possible.

I hope things improve for you soon....