always paranoid about the bf...... please help :/?

me and my bf have been together for almost a year and we have maintained a great peaceful relationship... until recently that is.... i dont know why but every time he talks/ associates with another girl i get so nervous and paranoid.. it is really putting a strain on our relationship b/c its causing us to fight all the time. i dont want to be jealous like this but i dont know what to do anymore. people tell me not to worry and calm down but i want to its just something inside that keeps bugging me. he has not done anything really to prove to me that he has been or will be unfaithful to me. i understand that im the one that needs to change/ fix this issue but it is really difficult and frustrating. please help? thankyou.