preventing unwanted precum

Hello, i am a 20 year old male.
When simply hanging out with my girlfriend, such as going to the pub or whatever, I will often leak precum. This is uncomfortable and happens without having an erection.
how can i prevent this?

This sounds pretty normal to me.

If it is leaving stains or wet spots on your pants you could wear a condom or wrap your penis with a handkerchief or other padding to absorb the flow.

D

This is telling you that your girlfriend excites you. (or something else does) Pre cum is a prelude to ejaculation and stimulation. She is stimulating you mentally, which your head is telling your little man that you are turned on for some reason. Hence, he starts to drool. You can't really prevent it, as a man's penis has a mind of its own, for sure.
If you see a hot chick, scantily dressed, you get aroused, enter pre cum. If i see a hot guy, scantily dressed, i.e. a beautiful well tanned construction guy in jeans, a wife beater, sunglasses and a hardhat, yikes...i get a little moist in the business area and there are times when my nipples will get erect. Can't help it, we love to look at beautiful people.
Wear dark pants or boxers so your boy is able to hang low, the when he dribbles it might not show up on your pants but on your leg. lol...