Masturbating: Cannot cum. I know that I am using good technique when I masturbate

Hi, I am 17 and every time I master bate I do not cum. I have definitely hit puberty (many pubes, some facial hair, stomach hair, armpit hair, deep voice, etc.) I was circumcised nearly a year ago, so I do not think it affects what I am about to say. It feels really good, but I never get to the point where I cum and once I start getting bored, I try to squeeze it out hoping I will cum but instead pee comes out (not concerned about this because it is towards after i am done jacking off and my penis is half erect). I have had many wet dreams (once every 1-2 weeks), but I cannot figure out why I cannot cum. My girl has given me head and hand for over 20 minutes and she found it weird that I did not finish. I know for a fact that I am not gay, and I also know that I am using good technique when I masterbate. Can someone please help?