I see my "ex" every single day—help!

Hi everyone!!

So, I’m taking a course and this guy is in my class. We never officially dated, but we had a romantic thing going on until the middle of this year. He ended—well, ended the thing that never really started—for a personal reason of his own. But since we see each other every day, we still show each other affection, and it’s really hard to pull away. He says he likes me, but I don't see much initiative from him to spend extra time with me; he always dodges it or makes excuses. Recently, he’s been hanging out with another girl. I asked if he was seeing her, and he swore to me he wasn't, but I found out they go to church together every Saturday (because *she* invites him) and leave together on Thursdays. Yet, he still says he likes me. What should I do?