Could I be pregnant?

My SO and I had sex during my fertile window about 3 1/2 almost 4 weeks ago unprotected. I am on birth control but for the week before and of us having sex I was on a antibiotic which defeats the purpose of birth control.  Within the past week I've felt so bloated and tired. I'm constantly hungry and very emotional. I've been so nauseous with horrible headaches.  My best friend told me to wait and see if I miss my period but I won't have one this month due to my birth control. Is there the chance that I could be pregnant?