At what age should I be able to pull my foreskin back

This is perfectly normal for about the first 2 to 6 years. By around the age of 2, the foreskin should start to separate naturally from the glans. The foreskin of some boys can take longer to separate, but this does not mean there's a problem – it'll just detach at a later stage.

Explanation:

you may having too much sleep.. a good night sleep consists of about 7 hours. more than that could be the reason you're still tired throughout the day.