Do I have insomnia or is there something else wrong with me?

I have a hard time falling asleep...some nights it can take me up to two hours to fall asleep. However, once I am asleep I don't wake up until my alarm goes off and sometimes I sleep through that. Because I sleep so soundly once I am asleep I'm not sure why I have such a hard time falling asleep, especially since I'm like always tired. Any ideas???