Relationship advice?!

Hey ladies and gents. Having a really hard time emotionally and would love some feedback.

My current partner and I met in March, didn’t have sex until mid May. A couple months of just friends hanging out and getting to know each other. After we had sex he said he wasn’t really looking for a relationship because of upcoming travel plans. Those plans fell through in June and ever since he’s been spending a lot of time with me and we started dating in July when he introduced me to his sister.

We now live together, because he lives so far away it made more sense for him to move in, he helps around the house, but has very scarce income right now. He buys groceries but that’s it.

We recently had Christmas at his grandmas house and got super drunk. I put him to bed and noticed his phone was going off and tried to wake him incase it was an emergency, but he wouldn’t budge. I opened the phone and found texts from his ex who cheated on him and had a baby with another man. He rarely talks about her to me. He’s ignored her since sept. 2, but the previous messages were a little concerning. He’d talk about how she’s the love of his lifetime and he’s sorry he can’t be there for her, pretty much texting her all summer.

I confronted him about it and he said he’s been ignoring her and he harbors resentment for her, that he’s loyal to me. What should I do? Move on or break it off?