How can I stay with my bf who emotionally cheated on me?

Hi all,
My bf and I have been together 1 year and half and our relationship has been great. We would have arguments here and there but we were always together for the most of part (we've been living together). I know my bf loves me very much and I am really close with his family. My bf always told me that he is gonna marry me and that's the end of it. However, few weeks ago, he started to get txt msgs around 6am from some girl saying "gmorning baby" or what not. For few days, I tried to tell myself that she might be a friendly coworker. As the stupid txts continued for a while, I confronted him and told him I need to check through his cell phone. And I did check through his cell phone and guess what...all the msgs with that person were gone. He said he deleted all that msgs in case I get upset but seriously I am not the type of girl who gets upset from my bf talking to other girls as long as it's within the boundary. I told him to tell her not to send txt so early or late at night since we are living together and it's kinda rude. But few days later, he got the txt from the same girl at night and this time I got pissed. That day, I checked through his phone - txts, phone calls, and everything. I found out that he was flirting with his ex and other girls as if I was not there. Even though his ex knows I am with him, he would ask her to come to chill or say that she was in his dream. I am not so mad about the fact that he's been talking to his ex but it was sad that he initiated all the moves towards her. For other girls, he pretended as if we broke up and told them how previous relationships with them were better than the "supposedly broken" relationship we were having that time. After that I got really upset and mad so I needed to kick him out (anyways I've been paying all the rent). He begged me to take him back and since I really love him I took him back. But ever since we got back together, I don't feel happy anymore and feel secure about our relationship. It's gonna really hurt to break up with him so I don't know what I should do at this point. Will I be able to get over his emotional cheating and stay together?