Hi, I Am Really Concerned About Being Pregnant. I Have

Hi, I am really concerned about being pregnant. I have 5 children with my ex husband and we recently were active couple weeks ago. I have not had a missed period yet only because we were active right after I ended my period between 1 to 2 days after. I wanted to take the morning after pill but didn't, I checked the ovulation calendar it says from my information that I entered that I would be fertile on the 9th he ejaculated in me on the 6th I am very concerned about being pregnant how soon can I find out before the missed period, I keep getting nauseous not sure if that's from stress or possibly being pregnant. Please help Thank you!