Missed period, PMS symptoms

Patient: Okay here is my situation, I am really scared and nervous right now. Me and my girlfriend are both 18 and we had sex for the first time 6 days after her expected ovulation date. Here is whats scaring me though, before we had sex i accidentally put the condom on the wrong way and then flipped it around before sex. now i do not know if there was pre-cum or not on the condom and i should’ve just thrown it away, but i was not thinking. it has been a very stressful month for both of us and she is now 6 days late on her period… so we are stressing out even more and are both very nervous because we do not want a kid. I heard that stress can delay or make a period even be missed? she was sick for a week or so before her period, and i heard that can also delay it. the last factor i need to say is she is taking Prednisone right now and i have read that antibiotics and that type of steroid are known to cause messed up periods. how worried should i be at this point because i am really freaking out and so is she?