Hi lil75. This could be due to a number of factors - psychological or physiological. We sometimes refer to our mind being "in a whirl" because of insoluble problems and it might be that you work yourself into a frazzle at the quiet time of the day, just before sleep gives you some relief. Alternatively, you might have an inner ear or sinus infection which applies pressure / creates dizziness when you lie down. Perhaps you've had a cold recently? My suggestion is to see your GP and get the physical part eliminated before you and the GP discuss the potential benefit of some counselling if you don't have a really good friend with whom to share your anxiety. In the meanwhile, try to square any issues on your mind well before bedtime. I find writing down an issue and my conclusion downloads the stress and lets me rest easy.
Wishing you well.