Should I text him?

So my bf and I just broke up. This guy I had a thing with last year texted me and kept talking to me asking if my boyfriend and I broke up, I said yes. The convo continues and I ask if he’s still with his gf, he is. But he says she doesn’t mind us talking and he sent me smiley faces and saying he likes talking to me then he asked if it was weird he had a gf and we were talking and I said no I just didn’t wanna cross boundaries or upset her and he’s like I promise you won’t shes not like that, I like talking to you. But anyways, that was this weekend and we haven’t talked since. I reallyyyy wanna text him but also don’t because I don’t wanna be the girl that ruins relationships. Also kind of wanna ask him why he did just text me. But idk if I should just leave it be or text him. Him texting me again brought back flashbacks of us being a thing and those feelings for him...

Also we have class together and he looks at me but doesn’t say anything.