1. I'm exhausted. 2. I'm dead tired. 3. I'm pooped. 4. I'm spent. 5. I'm beat. 6. I'm running on fumes. / I'm running on empty. 7. I can hardly keep my eyes open. 8. I'm off to bed. 9. I'm gonna hit the sack. (hit the sack = go to bed) 10. It's bedtime for me.