my girlfriend told me today that she's had brown spotting for the past 2 days and that her period is supposed to come today but she has irregular periods so that's not for sure

but she told me that she has normal pms symptoms, the ones she always has when she has her period

I 100% always use a condom and I always check it afterward, I've never had a leak or a tear visible to me...but besides that, what is the likelihood that she's pregnant?