So me and my boyfriend had sex the end of dec and then I start my period like 4 days later then now I've been wait for my period could I be pregnant?

Possible? If you have had unprotected sex, you can be pregnant. No one can say without testing. You situation would place you in the non-pregnancy time but unexpected things happen! if you are late, just check it out.
Check a test. Easiest way to answer that is to check a urine pregnancy test. If you're pregnant, it will usually be positive by he time of a missed cycle.