Plan B Pill

My boyfriend and I had sex. Im not on any type of birth control because the last one I was taking brought down my sex drive and had water retention which was making me gain water weight. We have a 15 month old. We don’t want to get pregnant again at the moment. This morning we had sex but we were both really into it that he didn’t pull out. (Which he normally does). He was deeply sorry since he knows that we both agreed to give it some time before we have another child. He cummed in me. We went to get a Plan B pill like 2hours later and I took it right away. I ended my period about a week ago and now I’m worried that I’m in my ovulating stage when he cummed in me this morning. Has anybody ever experienced a similar situation on counting for the Plan B pill to work? Im worried that I’ll get pregnant. Thoughts? Im just wondering how effective is plan b on stopping from me getting pregnant.