How can I sleep at night?

So I'm in 7th grade and I just can't sleep! I've had this problem for a few months now...I always read before bed and sleep with a small light on. If it makes a difference I do have a lot of fears like murderers and burglars etc. Sometimes I know it's because I wasn't stimulated enough but on some days (like today) I do exercise etc... Right now it's 1 am and I went swimming 5 hours straight today! I eat healthy and am in pretty good physical condition. One of the things that sometimes effects it is if anyone else in my house is awake. If my parents are awake then I can usually sleep. I don't take medicine except sometimes natural things like Rescue. If I'm up all night I'll usually watch videos on my laptop or something. But I really want to sleep already!! If you could suggest something it would be a great help.