Can draw, but have no foundation to speak of. Help!!

Hello. My name is John. Ive been drawing since kindergarten, so I'm not new to the subject. I took some art classes in junior high and high school, but they didn't teach much. I not so much as self taught as others. I'm pretty much almost able to draw what I see, but that's even limited. I'm hitting a wall and having trouble getting back into drawing. I've been trying to use sights such as "http://artists.pixelovely.com/" to tray an get back to drawing, but it's not working as I expected. I guess you're suppose to keep at it until you get it, but that's kind of discouraging. I was wonder if' anyone had any suggestions to get so I can get back in to drawing and creating a solid foundation to start off on? I want to go back to school but I don't if that would be a waste of time and money. I've attached some old drawings I have done, they're not complete or perfect though. I hit some dead ends on two of the because I don't have all the necessary skills to finish them. So if anyone could give some helpful advice, I would much appreciate it.