Insomnia

I have had a problem staying asleep for almost two months now. I have insomnia and I don't know what is causing this problem.

1. I am eating healthy foods.
2. I am eating reasonable portions.
3. I exercise almost every day.
4. I don't feel increased amount of stress in my life compared to when I was sleeping well.

Last night was one of the worst nights I've had since this started as I was laying in bed for hours trying to go to sleep with no success. I feel like hell today and don't want my fatigue to overwhelm other parts of my day-to-day activities.

I'd strongly prefer to not take medication to combat this.