Plan B baby

Hey everyone so recently my boyfriend and I had sex, Saturday May 16th. Anyway we had sex up until Sunday May 17th because it was late. Either way we had sex but he came in me. On my app it said that I was in my fertile window and I didn’t take the plan b until Tuesday May 19th. Ive also heard if you take the plan b during your fertile window it doesn’t help anything because you’ve already started ovulating. Is this true? And has anyone had a plan b baby? If so can you leave your stories Below?