15 years old with penis problems.

Im 15 and started pulling my forskin back about week and a half i think, and at first it was painful and i could only pull it back a quarter of the way when erected and now i can almost get it over the whole head when erected :-D but its still a bit sensitive and i can pull it back all the way when its soft but im always afraid im not going to be able to pull it back over the head and ill get a random boner and the skin will like rip

but yeah, i just pulled my foreskin back as far as it could go everyday and its almost all over.