What Causes The Formation Of Extra Foreskin At The Penis Head?

hi doc
i m 25 yrs and had a tight foreskin...i am streching it from past 1 week and results are positive. but the problem is that i have got extra foreskin which forms a bundle at the end of the glans when my penis is erect...if i try streching it further it hurts. if my penis is not erect i m able to strech it till the end but while erect i m unable to strech it ... i have problem in masturbating as the ring of the foresking got tight at the end of the glans...please suggest as dont want to go under knife....