Chances??

I normally have between a 28-32 day cycle, but am now on cycle day 40. My AF was due 2 days ago. I normally get cramps, constipated, and have very tender breasts before I get my period, and none of my normal sympotms have surfaced. I've been feeling slightly nauseous for the past few days, been having lower back aches, and I'm always tired. I took a test yesterday and got a BFN. What are the chances I'm pregnant? We are trying, but I don't "feel" pregnant, nor do I feel like my AF is coming anytime soon.