I had sex about 3 weeks ago. we used a condom and he pulled out. Last month I got my period on the 14th however it's never on the same day each month. I recuently travelled out of the country for 10 days the previous month and I also had a yeast infection and was sick so I had to take antibiotics. I've been under some stress with my dad in the hospital. Could all of that cause me to miss my period? What are the chances that I'm pregnant?