Oh, and I am a firm believer in exercise. It makes us do everything else better. We sleep better when we exercise. So, incorporate exercise into most days of the week or increase what you are doing a bit and see if that doesn't help you relax your mind. good luck
Our minds can be so noisy and frankly, such a pain at times. Don't you wish there was just an 'off' button? What about trying some form of meditation when you go to sleep. Repeating the same things over and over. It could be a prayer or a poem or something. And then you think less because you lose yourself in the thing you are repeating. You could try reading a good book as well. I do this and I'm one to get REALLY sleepy when I read at bed time. I have the light in arms length, switch it off, throw the book next to the bed and off I go. So, maybe try something like that.
You can stop by just stopping. If you can't just stop, then you might be developing OCD. What will happen if you just stop is, at first, you will be nervous and might lose some sleep, but hopefully over time you'll just stop doing it. But if it is OCD, it is hard to get over, because if you do it you spend time on the ritual and if you don't do it you get very anxious. If that's what's happening with you, it might be time to see a psychologist for some help in learning techniques to get you past this way of thinking. But if this is your only manifestation of anxiety, I'd first try to just stop doing it -- when you say you "can't," of course you know you can, but it will be hard. How hard only you know. The harder it is the more likely it is that this sounds like OCD.