mylan ?

So I am 3 months postpartum and have not yet received my period so I decided to pick up my mylan Birth control pills ..: I had a test and ultrasound done before my doctor gave me the okay to take them thing is Thursday night me and my s/o were having sex and the condom got removed from him and how some ended up inside of me so as he was cumin some got in me .:: but I had the condom in there to so there was not much that went up there cause I usually have a discharge the day after or later on from his sperm my question is would it be okay to start my mylan birth control or should i wait I'm also on antibiotics so the pharmacist said to use a back up method until I was done and 48 hours after I'm done with my antibiotics