I have the same problem...but I can only get really shit hash so If I smoke a joint the first night it will knock me out but a few nights after that i hardly feel stoned off it at all.

Its mostly my thoughts that keep me awake...but I move around alot aswell which keeps me awake and I wake up multiple times in the night...

I actually made a thread on this alittle while back...you might find somthing useful there
http://boards.cannabis.com/showthread.php?t=39874

hope this helps dude