Hi Im Mackie. My Girlfriend Has Irregular Period.. Its Been

Hi im mackie.
My girlfriend has irregular period.. Its been 6 months since she doesnt have her period just small blood she called spotting.
we have sex yesterday and i think i cum inside her and im not quite surr. But a few hours from our intercourse.. She bleed like she has a period. And she told me that she will not get pregnant because she bleeds. Is it true ? I wanna make sure.. Is she not going to get pregnant ?
we dont wanna have a baby.. We're still students..
I hope this hepls.. Thank you :)