I am 16 years old: when erect only half of the tip of my penis shows. I was just wondering if this is normal? I thought that when your penis is erect that the entire tip is exposed, then when non-erect the foreskin retracts to protect the tip? Am I right or wrong? When will my full tip come out? Or do I have to pull my foreskin back during intercourse? Thanks!

I'm a 17 year old male, and when I'm with my girlfriend, I can't always get an erection, and it doesn't always stay up. Also, I am an uncircumcised male, and when my girlfriend rolls back the skin and touches the head of my penis or when she gives me a blowjob, it feels really sensitive, almost to the point where it hurts to touch it. Is this normal?