Couldn't Fall Asleep

I am so tired today beucase I had a hard day yesterday and Icould't fall asleep last night.Monday is my busiest day in a week. I go to the school in the morning and I have to work in the school library lab and after the school job I have to work in the restaurant until 9:30..Usually I will get really tired at the end of the day, so try to sleep early in Monday night.. I really didn't know why I couldn't fall asleep. It usually happens when something happen to me and I keep thinking of it, but not this time... There nothing special happen to me in the last few months. I went to sleep at 11:30 p.m last night, and I think I fell asleep at 1:00 a.m at the morning. Also, I woke up three time between 1:00 a.m-5:00 a.m and that means I didn't sleep well last night...However, I tried to take a nap to make up my sleep when I got home(around 5:00p.m), but I just find out that I can't fall asleep again. I can say that I couldn't fall asleep in last night might because the weather(because yesterday was hot and the air was sticky too), but I really don't know why I couldn't sleep today..It's nice out side today...