So my SO and I had sex for the first time Dec 29th. We used a condom. The second time was around January 14-? And we were unprotected so I took plan B. The two other times after that we were protected. But recently on the 2nd of Feb we were unprotected again but he withdrew before the precum and then semen came. My periods have started to regulate and they come about every 35 days but this months hasn't shown up. I've had some cramping but that's all. No nausea or tender breasts. I have back pain but I've always had back pain. Could I be pregnant? What are my chances? Any ladies had this experience? Is it just the Plan B?