Since she was having a period, it is pretty unlikely that she would ovulate within the time period when your sperm would still be alive. Not impossible, but less likely. Try not to stress, things are probably fine. (But don't be casual about protection any more, either, no matter what time of her menstrual month it is.)
Of course this is always possible, although the fluid you encounter prior to ejaculationis from the seminal vessicles. This is primarily for lubrication and shouldn't contain any sperm. But beware, this is a gray area and it is always possible some sperm can travel into the fluid, since ejaculate is a mixture of 3 fluids, prostate, semen, and seminal vessicle fluids.
Best regards
While it is unlikely, a girl can get pregnant while on her period because sperm can live in the vagina for a few days.
Since it was unprotected for not very long, I'd say you're probably safe.
However, please know that precum CAN contain sperm whether you urinate or not.
Good luck and Best wishes! :)