Freaking out

On January 28th I lost my virginity to the love of my life. I was on my second day of ovulation. All he did was put it in and then took it out immediately. The next day I got on nexplannon, which is a a type of birth control that is inserted into the arm and lasts for 3 years. I am supposed to start my period tomorrow, but I'm so scared that I could be pregnant, and yes I know it was a huge mistake to let him do that without protection. So far, I haven't had any signs of implantation (no spotting), or any other signs such as headaches, weird cravings, nausea, ect. I haven't had my normal period symptoms either. My breasts are sore but normally my lower back hurts when I'm about to start. I'm not sure what to do or what to expect because I'm completely new to birth control. What is my possibility of being pregnant?