whoa dude. thats pretty awesome! how long have you been drawing?
you kinda remind me of me when i started out. (not all the way back in 5th grade, but like when i started to understand art concepts)
you face the same problem that i did and still do now. the head is kinda big, but its not that big of a deal. i also like the arms. they look well proportioned for the most part, but are his shoulders supposed to be like that? oh well. but hey it looks good dude. i think you should probably look at working on hands though.
but like i said. good job.