bf following his ex on ig

Hey, so my bf followed his ex on instagram : I know i might sound petty but I feel like it isn't ok at all! I let him know how I feel and he apologized and told me he will unfollow her later I also learned that he like her pi. I know I shouldn't be insecure and stuff but that really made me feel sad and just I don't know how to explain it I'm feeling insecure and betrayed? Idk what do you all think ?