Post partum pregnancy?

I had a c section 11/25/2020, bled for two weeks after, stopped for a week, got my period 12/24/2020 which lasted until 12/30/2020, My Fiancé and I had unprotected sex last night and he finished in me. I had taken a plan b about a week ago as well. I’m scheduled to get the nexaplon BC this week, would there be a high chance of pregnancy & would I know prior to getting BC put in even though technically I’m not supposed to be sexually active again yet. Plz share stories if you have a relevant one as well, TIA