Please help...

So my boyfriend and I have been talking for a year now and we have been dating for 3 months ... but se have had a lot of ups and downs like really big ones and I’m trying so hard to work on us and fix us but sometimes I feel like he doesn’t care and doesn’t try ... for example one time he left his phone with me he got a message from a “ guy “ saying “ we should meet up again “ and ended up being a girl he just met ... and he was flirting with her and kept denying it after the proof and the truth was right in front of us anyways ... I let it pass but things like that keep happening and he gets mad at me and says that I should get over it .... but when I ask him to please talk about us and how it’s going basically talk seriously about us he says he really wants to be with me ... but he does all those things and idk how I feel ... I’m tired of all the lies and drama but I love him ... what do i do?...