Question: No period but BFN!

Hi guys. So 5 weeks ago i came off the pill. I had a withdrawal bleed and we started trying for a baby. Judging by the cycle i had while on the pill i was supposed to get my period 6 days ago. But still nothing and the tests arw negative. I have been feeling a bot naseous, get headaches, really bad backache and cramps. Is there any chance i could be pregnant even though the tests say im not?