>>29261498There's a simple physical reason for it. There's nothing wrong with you.
Your muscles are fine, you don't need to keep yourself from jerking off, because nothing you do won't help you.
Next time when you go to shower, put your thumb on the faucet. See what happens? Water will jet out of the faucet.
It happens because the diameter of the faucet is then much smaller.
Your urethra is just a bit too wide and that's why you can't put any pressure in it, no matter what. Just accept that your cock is like that. If you do get an erection and you can masturbate regularly and you have no problems getting an orgasm, then you're perfectly fine. There are many porn stars who aren't shooting properly either.