What Causes Delayed Menstruation With Abdominal Bloating And Cramping?

Hi there, I had unprotected sex about three weeks ago. He used a condom, but it broke and I'm not on any type of birthcontrol. I made him replace the condom, but it broke in the end so he just removed it. He used the withdrawal method when ejacualting, bu lt I decided to take the generic brand of Plan B. I took it within 12 hours of intercourse and I haven't had a period yet. I am extremely bloated and have had slight cramping in my lower abdominal region. I don't seem anymore fatigued than I usually am and I go to the gym frequently. I haven't felt nauseas either. I've taken two pregnancy tests and both came back negative. Is there a possibility that I am pregnant?