Instead of normal urine, it was like a completely white liquid, and it was quite sticky

Hey there so first off I wouldn't say you are delayed puberty but are developing normally. Have you tried masturbating  yet? If so have you noticed any clear or white sticky liquid coming out of your penis.  When you woke up was there sticky fluid in your underwear or bed sheets?    It is normal for you to have difficulty peeing with an erection. When you get an erection a muscle tightens near your bladder to prevent semen from flowing into your bladder instead of out your penis.

So I have tried masturbating in the past, but I was circumcised when I was young and I don't know if it's that or something else but I just don't get any sense of enjoyment from it. And no, there was no white liquid in my sheets or underwear

How have you tried masturbating like what techniques. Also have you ever tried any type of lube?