may I be pregnant?

Ok so I had my period in October on the 24th and it lasted about four to five days. Then I had my period in November on the 20th and it lasted about the same. Well I figured my period would come on the 20th again. So me and my husband had sex on Dec 19th and I let him come inside of me and I am not on any medicine. I still haven't got my period yet and it's the 22nd. Could I be pregnant?