Trying so hard to sleep that i cant sleep?

Last night i went to bed around 12 am because i wasnt feeling so tired but when i was lying down, something didnt feel right. I was still awake after 45 minutes. So i tried my best to sleep but i couldnt. O guess i was concentrating so hard to sleep that i just couldnt sleep? It was so bothersome i started thinkinh about sheeps jumping over a fence... Yes i know but i was frustrated! I then realized it started getting bright outside and my alarm clock said 5:40 am. I started panicing because i thought i would never fall asleep again and die of exhaustion :( i then fell asleep and woke up at 8 to take my pills. I never have sleeping problems ever and just like that i cant sleep. I felt tired but i just wouldnt shut off :( im really worried about tonight now. Does anyone know why this could happen? Please help?! By the way im a 15 year old guy and ive been taking antidepressants for over three years but never had problems sleeping like this :(