Well considering your height I would either say defensive end or outside linebacker depending on how fast you are.
cornerback or safety
If you can put on 30 to 40 pounds of muscle you can play running back
defense of end
I think you should be a running back because you're so fast.
Quarterback or Halfback.
your tall and your pretty light. you should be a wide receiver
MLB if ur gud
Kicker or waterboy
I would say wide receiver or cornerback
A corner Back or defensive end.
If your fast: cornerback or wide receiver
depends on what you're good at. At 5'8, you should probably try running back because most little men have a better advantage of getting around their opponents that are bigger than them. Think about it.
In 7th grade you would probably be an offensive or defensive lineman.