The Ex..😩

So there's this ex, whose going through it right now. For the past 3 days or so I've been spending time with him... here's the thing I have a bf, he doesn't know. I still love my ex and he said, "I should've kept you around, I needed me a girl like you" a few moments later he started feeling on me, I told him to stop but I really liked it.. I do care about my bf, I don't want to hurt him at all. I've been with my bf for about a month now. My ex I've dated off and on for almost two years. What should I do??? I haven't talked to my ex since way earlier today.. should I tell my bf the truth???Â