I have not seen the head of my penis and I am 17 years old

I am uncircumcised and I know that a normal uncircumcised person can pull back the foreskin to see beyond the head of the penis. But I never actually tried and just threw off the idea, I was talking to my guy friends and dont ask how we got on the topic but all three of us are uncircumcised and they can all pull back the foreskin a decent amount. I admitted I never tried and they started telling me all of these horror stories but were being completely serious and told me I should probably see a doctor. Everytime i try and do it i just mentally psych myself out of it and barely pull it back. Like just enough to see a small portion of the head of my penis until I pussy out. I dont know what to do 

Do you know what stops you continuing to try to retract your foreskin? If it's very tight, and / or hurts, you are right to be cautious. However, gradually pulling back a little more each day will probably help. If not, get it checked by your doctor. They may be able to prescribe a cream for you to apply.

It's called "phimosis", and if you're only 17, then depending on how tight your foreskin is, it may just fix itself, but gentle stretching and possibly a steroid cream will probably help.  If you're in the US, you can get 0.05% betamethasone cream without a prescription, but if you can't fully retract when soft, you may need a stronger strength, which you'd need to see a doctor for.

Roughly how far in mm can you open your foreskin when soft and when hard?  If you have pinhole phimosis, then I'd try gentle stretching and steroid creams first, but if that doesn't work, then surgery may be required, which could be preputioplasty, a dorsal slit, or circumcision.  Don't try to it too fast.  Gentle is key, and even if it seems to be giving quick results, don't overdo it.

If you google "phimosis stretching" or search this forum, you'll find lots of information from people who have fixed phimosis, even when they were told they needed to be circumcised.  Some people will need surgery to fix it though, and some people choose to just live with it.  Personally I would want it fixed, even if it required surgery - it's difficult to keep clean if you can't retract (which can be a huge turnoff for a potential sexual partner), I don't see how sex could be as enjoyable if the inner foreskin and ridge of the glans are never exposed, and phimosis is linked to higher rates of penile cancer

NORM-UK have a retired GP who specialises in cases like this.

This link is written for doctors, but may help:

https://patient.info/doctor/phimosis-and-paraphimosis