if a liquid came out of your penis.....most likely it's precum and it DOES contain sperm and even by mutual masturbation it could (it's rare) cause her to become pregnant. get a home pregnancy test. you can buy them at dollar general, wal mart, eckerds, giant eagle, shop n save, kmart.....pretty much any supermarket, convenience store or pharmacy. they range in price from $1 at dollar general for the generic brand to $13 at wal mart for the digital tests.
The liquid you are referring to is pre-ejaculate which does contain a small amount of sperm and therefore can result in pregnancy. The method you are describing is unlikely to get your girlfriend pregnant but it is still a possibility.
A home pregnancy test can be purchased from a pharmacy or supermarket for a few dollars (by feminine products section). Basically it is a stick she pees on that can detect the hormone HCG that is produced by pregnant women. The home test will be effective about 2 weeks after possible conception although it can take a little longer to get a positive result for some pregnant women.
btw: since you are a male, YOU cant get pregnant.