Help!! Late period!

My fiancé and I last had sex on Nov. 10th. I got my period Nov. 17th after a super stressful week of waiting, it was bright red, heavy with clots for 3 days then lighter for 3-4 days before stopping.

My period this month was due on Sunday Dec. 15th. Today is the 17th and there is still no sign of blood. I started getting cramps/backaches on Saturday, usually I get them a week prior to my period. Also had some "false alarm" moments yesterday.

Am I pregnant or still stressed?

Please no comments about Plan B. We have our reasons why I didn't take it.