brothers girlfriend telling him to break up with me . his ex is he

so I’ve been with this guy for about almost 10 months now .. and I just found out that his brothers girlfriend was telling him to break up with me and go for his ex. Well his brothers girlfriend is cousins with his ex. she told him that his ex is prettier than me and that just makes me think that its starting to change his mind about me . we recently got in a fight this weekend. he used to not hang out with his friends that much because he beleived they didnt treat him right . but not all of a sudden he wants to hang out with them all the time and they keep calling him up . I want him to hang out wiht his friends .. dont get me wrong but one of his friends girlfriends is friends with his ex . and I think thats just making him get closer to her and change his mind ..im getting a little suspicious about it but I dont want to .. he kind of acts different to me in a way like he doesnt care that much . and now since we fought it only made me stronger and relize I want to be with him .. I dont know how to act towards all of this .. can somebody please give me advice about this . because I dont know if I should bring it up to him or just keep it to myself. idn thanks a lot!