I went off birth control pills in May. Every since i have started on the 10th. My husband and I don't use protection. My last period was on Oct. 10th. On nov. 10th when i was supposed to get my period i had slight cramping, nothing like usualy though. And lower back pain. I have been feeling nauseous, but i think it's in my head. It's Dec. 4th and still no period. I have taken many hpt and all are negative. Could i still be pregnant? Is this common?