[Harmony♥]

While it's true that pre-cum can get someone pregnant, the chances of getting pregnant from your situation are slim to none. Pre-cum doesn't automatically carry sperm. The only time it does is from a previous ejaculation you had that day, when left over sperm would be left over in the urethra. Since you mentioned you didn't ejaculate that day, and had urinated, pre-cum is something you don't need to be worrying about, much like pregnancy.

She mentioned it herself that her period is irregular, and two days late is really nothing to worry about, especially when you know that her periods aren't very steady. I would calm down, relax and try to help her calm down and relax. I'm sure she's terrified right now about what happened (any girl would be, especially if there is a possibility of pregnancy), but stress and worry can also cause her period to be a little off course. So, remain calm.