Could I be pregnant? Whats wrong with me....

Ok, so I had an "oops" with my boyfriend last Sept. and we resorted to the Plan B pill. Before the incident, my period had always been on time, a medium to heavy flow, and between 5 and 7 days in length. Every month since I've taken Plan B my period has been on time, but only lasting 2 days or so, and my flow has been extremely light. The last period I had started between January 4th and 7th, and ended 3 days after it began. (I know, stupid. I should keep track of exact dates). Well, my boyfriend and I have not had full on unprotected sex since then, but we have messed around a couple times (only lasting max. 30 seconds.. maybe less) before he put on a condom. He never ejaculated until after he put the condom on, but here I am .... February the 11th and still no period. I took a HPT (Clear blue easy digital)  on the 8th and it was negative, but I'm not sure if I can truly rely on that. I DO plan on retesting again this weekend with the other test. My breasts are always sore up to a week before I start my period, and I have no sign of this .. or my usual mood swings or headaches that come along right before it happens. I'm really scared, seeing as how I don't want to be pregnant .. and just wanted to know if there were any educated thoughts out there about what could be going on? Could I seriously just be psychotically paranoid?... Thanks for your help :-

Sperm can still be in the pre-ejaculate so even though he may not have ejaculated in you, there could still be the chance of pregnancy. I would go to a doctor as their tests are more sensitive and they can check to see if your uterus is enlarged at all.

See more answers here