My foreskin doesn't retract when I get a erections. I can pull my foreskin back when erect though, but after the erection is done, my foreskin doesn't go back to cover the glans. Do I need to get circumcised?
You do not need to be circumcised. I suspect that the opening of your foreskin is mildly tight, not enough to cause problems, but enough that it needs a little help. After erections, you just need to slide your foreskin back into place. You don't want to leave the glans exposed because the tightness of the foreskin can interfere with blood flow. However, if it is left exposed for a short while, it won't cause any harm.
You can also use the stretching exercises to see if you can get your foreskin to loosen up more. See: I can pull my foreskin right back, but when it is pulled back it is really tight