I am born dec 20 Sagittarius end on 21 I am nothing like a Sagittarius and way more like a Capricorn would that because I am so close to the end?

This would mean that you were born on a "cusp" or on a day where sagittarius was still transitioning to capricorn. So this means that you have triats of both signs. (And no I am not an astrologer. I just know things.)