I had an unprotected sex last dec 24 on jan 3 I experience a very light period which is not normal for me. Could I be pregy?

Light period. Pregnancy should always be considered in women who might be. Especially if there are any changes to the menstrual pattern or pregnancy symptoms. Do a test and get checked by a gyn.
It's possible. But if you want to be sure, I would recommend purchasing and using a home pregnancy test. Good luck!