plan B

Me and my husband had unprotected sex last week on Wednesday and he came inside me. I checked my glow app and it said I was on my first day of ovulation. So we got a plan B pill and I took it that day. Well I started bleeding on Monday. And it's like a full fledge period. Not to mention I just had my period at the first of the month. Anyone have any insight on this? This is the first time I had ever taken one so I wasn't sure of the side effect. (No need for rude comments as I am fully aware of my decision to take this pill)