Overthinking I think

I’m freaking myself out. So I’ve been on birth control (Junel Fe 1/20) for nearly 7 years. I’m very good about taking my pill daily. Well last month (April 8th) I had sex. I’m pretty sure he pulled out in time being i seen him. It was the day after my period ended. Due to being on birth control, I know I technically DONT regularly ovulate, but my chances of it did occur are slim considering when I tracked ovulation it said my fertile week was the week of April 16th. Toward the end of the month I got a throat infection as well as was VERY STRESSED OUT about finals and the possibility of being pregnant. The throat infection was awful and caused me to be nauseous and loose my appetite. I was prescribed prednisone and cefdinar. I was told the antibiotic would interfere with my birth control, however, I still bleed on my 7 placebo pills. I then had a normal week with no bleeding on active pills and then I bleed/spotted red for a week on active pills. My next placebo week starts tomorrow. I’m afraid I might not bleed and that will freak me out. My stomach and back have been hurting me but I’m thinking it could be stress or IBS. Help/advice?