Actually, I want to ask one thing. my girlfriend and I were grinding each other. She was nude and I was wearing my jeans and underwear. I ejaculated and it was on my pants. Since she was nude, is there any chance of her getting pregnant?
The sperm in your semen are microscopic, so small that they can move through the weave of clothing. The image here is that of silk cloth as seen under a high-powered microscope. Notice the scale at the bottom right. Each notch is 20 microns, so the holes between the weaves are easily between 80 and 100 microns. Your sperm, however, are only 5 microns wide.
Sperm have tails and are able to swim. So long as there is liquid, such as your semen or her vaginal fluids present, the sperm can move toward the uterus. Very few sperm would survive the journey, but it isn't impossible.
Because you were grinding, it is possible or even likely that at the point of ejaculating, then end of your penis was close to the entrance of her vagina. Thus, we can't rule out that a drop or two of semen might not have dripped into her vagina. The odds are slim, but not impossible.
Added together, there is a chance, though extremely remote, that you could have gotten her pregnant.
While pregnancy is a very remote possibility, there is something more important that absolutely did happen -- the two of you sinned. You might have been trying to avoid fornication (having sex outside of marriage), but you did not avoid lewdness (acting without restraint, like an animal). While you didn't put your penis in her, your thoughts and desires were to do just that, which is lust (a strong desire to do something unlawful, to the point of willing to justify doing the sin in your mind). "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). Because lewdness is a sin, the sexual touching that leads up to lewd behavior is also sinful. "Now concerning the things of which you wrote to me: It is good for a man not to touch a woman" (I Corinthians 7:1). Nor should your girlfriend have been exposing herself to you.
I hope you will consider this and change your behavior. Stop putting your girlfriend at risk just because you want to ejaculate. Stop putting your lusts ahead of God's laws. I would rather see both of you in heaven.