Does my boyfriend like another girl?

whenever my boyfriend see's this girl he acts different. about a year ago he told me that he went to the cinema with her and she tryed to kiss him but he wanted to but said he had a girlfriend. this girl used to be sorta close me like a close friend, but she knows that i dont like her and i think she dont like me. my boyfriend said that he used to have small feelings for her but not anymore but im not sure if hes lying? the girl really likes my boyfriend though :( she always trys to cause problems between me and my boyfriend and sometimes my boyfriend would stick up for her. once he lied to me about not coming out to a restaurant because he said that hes going to a party but then i found out he was with her. should i brake up with him?:'(