Post period

Hi guys very confused here I was under the impression if I hadn’t had a period since having my baby 7 months ago I could still get pregnant even tho it hasn’t returned, but my doctor today told me because it hasn’t returned there’s no possible way. Has anyone fallen pregnant before having there period return post baby?

I’ve had pink discharge type thing for 4 days but nothing when I wipe and on the mini pill also could this be a light period at all?