I wouldn't call it insomnia but back in my uni days, sometimes out of the blue, I had those days due to some inconvenience, I couldn't sleep all night and then slept like a baby in the early morning, and due to that my whole day wasted and because of that, when I again try to sleep as I have slept so much just 7-12 hours ago, the same f*cked up schedule continues. To overcome this, one day I was again not able to sleep all night but I tried not to sleep the whole day and later when it got dark I slept at 10 PM and my sleeping schedule started to get better. And If it doesn't work for you then I'd prefer you to have your favorite meal at dinner and don't be shy to have it full and you'll feel sleepy after dinner, you can go for some exercise or gym in the evening which will make you tired post session and have a relaxed sleep and I used to do both to get a better sleep afterwards.