Irregular period?

Hey y'all! So my husband and I had unprotected sex tonight, ( big no no ), I know 😞 my son is 6 months and we aren't ready for another but when I'm actually in the mood its hard to stop. I was supposed to start my period two days ago but I'm late. ( I've had irregular periods since I had my son ) what would you say the chance of me getting pregnant 2 days after an expected irregular period are? Would you pick up plan b in this case if you weren't trying to convince? Tyia ladies!