I generally masturbate once or twice a month. When I go with my girlfriend, we don't have intercourse, but as we are very close, I get the feeling of ejaculation but it does not happen. When I masturbate that night, it comes out in a pure liquid state and I get an extreme pain in my testis. Even my penis aches. I do not know what's the problem. I had the same problem several times. Could you please explain it to me?
Sounds as if you two are spending too much time cuddling and touching each other and not enough time getting to know each other as people.
What I suspect is happening is that you are staying erect too long because of your fooling around with her. The penis inflates with blood by keeping the blood from flowing back into the body. This makes the penis swell like a balloon and get stiff. However, there is only so much oxygen in the blood that is trapped in the penis. Eventually the oxygen runs low and you begin to ache. Usually erections that last longer than 30 minutes will cause this pain. Sometimes a guy is so caught up in the sexual excitement that he doesn't notice the warning signs. The ache is coming from your penis trying to recover from being deprived of oxygen for too long. The slang term for this is "blue balls."
Along with this, you are getting yourself aroused to the point that your body prepares for ejaculation. Semen is moved to the ejaculatory duct and the prostate gland adds a chemical to thicken the semen. But you don't ejaculate and semen eventually liquifies. When you finally do ejaculate, it comes out as a liquid.
Everything aches because you started the sequence for sex but stopped. Since you are not married it is wrong to have sex. But it is also wrong to start what you can't morally finish. The proper thing to do is not start. What you and your girlfriend are involved in is lewd behavior. "Let us walk properly, as in the day, not in revelry and drunkenness, not in lewdness and lust, not in strife and envy. But put on the Lord Jesus Christ, and make no provision for the flesh, to fulfill its lusts" (Romans 13:13-14). Sex belongs in marriage, and that includes what leads up to sex. You and girlfriend need to stop sinning.