Should i just leave him?? /:?

well ive been goin out with my boyfriend for 3 months now & i used to think he was amazing! i met him beacuse my sister and his brother are going out and have been for about 1 year now so i already knew him and really liked him soo they got us together. anyway i really liked him he's nice sweet funny gorgeous when he's with me+just me. ive never really hung around with him when he's with his friends because he goes to a diffirent school to me and at his school he's one of the popular boys but at my school i wouldnt say i was one of the popular girls but i doo have alot of friends and im liked by alot of people but not as much a him. but my bestfriend went primary school with my boyfriends bestmate and she didnt like him at all. she told me he was one of the horriblist boys she new and i wouldnt liike him but i thought he cant be tht bad.. but anyway my boyfriend came round myn with his bestfriends who ive never properly met before and acted like a ritee jerk! he was actin imature stupid and ratha rude it atually made me upset soo i told him to get out then the next day i went to his cus my sister was there and as soon as i got there he was with his friends again and he dint say anything to me he just gave me a hug and went out with his mates! :(all my friends keep tellin me to just forget about my boyfriend and ive realised what he's really like wen he's with other people and i dont like who he is. ive realised if he went to my school he would be one of the boys i would just wallk past and not talk to. but i really like him wen its just me and him he can be the best boyfriedn ever but i dont know what to do? help! :)X