Am I pregnant?!

My last period started October 27th and ended October 31st. I was supposed to start my period November 30th and still haven’t started but I’ve had cramping like it’s going to start. The past 3 days all I’ve been doing is sleeping or eating crackers because anything else makes me feel like I’m going to get sick or gives me heartburn. Am I showing pregnancy symptoms? When should I take a test?