yes you need to be able to see your penis head the skin should slip down easily
im 16 and this happens to me, i was worried that it might cause problems during sex...does it?
you can forcefully retract it, as i recently discovered, its actually the first time i have fully seen the head of my penis before.
it dosent hurt if you take it slowly, once u cant pull it down anymore you can pull the bottom side of it and it usually just slips straight down :S if thats any help at all.
if you cannot pull your foreskin back when erect you have phimosis but it is easily fixed.here are some links to show you how using stretching and topical steroids will help.
http://www.glansie.com/?gclid=CL7U756dq44CFQFZHgodLA90Sw
http://gfs.platigo.com/
http://www.norm-uk.org/foreskin_restoration_devices.html
http://www.medicinenet.com/betamethasone_dipropionate/article.htm
http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a686008.html
i also think iv got this problem, when im erected if still got alot of foreskin and when i pull it back it can go back over my head pretty easily (say when getting head), im not sure if this is normal or not