Should I be jealous about this?

ok, my bf, before he was my bf, asked out my best friend, and she said no, bec she already liked someone else. Now we are going out. and both me and brittany sent him this forward thing about what the first thing you thought when you saw me was, and he sent y to both me and her. This made me really jealous, and I didnt answer his calls for awhile. Should I have not gotton jealous over this? Oh and by the way im 16, my best friend is 15, and my bf is 17.