No, cannabis doesnt cause insomnia. Are you on any other medication. It might be because your smoking a sativa which is a heady high. Get an indica strain, smoke as much as you normally do, then lay down, listen to some music and you'll fall alseep. If that doesny help, then maybe you should see your doctor about pills. If you do, make sure you ask if smoking cannabis with them will cause any effects. He shouldnt mind that you smoke cannabis, if he knows whats he's talking about he'll know its actually healthy for you.