Relationship trouble¿?

So my boyfriend and I have been dating for a few months now, and he from time to time texts his ex girlfriend ( the one right before me). I’m not one to get toooo jealous so it didn’t bother me when she needed to pick up some things she left or even random updates in her life. Recently, I saw he was planning to go visit her at her new job and just because I don’t get toooo jealous, doesn’t mean I’m not jealous at all.

Obviously I ask him about it and he’s like oh yeah I’m not sure if I’m gonna go. And of course I’m pretty pissed and confused on why he didn’t tell me or why he would even be going at all. His response is that they were friends before they started dating. I then see that she’s asking him if he’s moved on and confirming that he broke up with her. Am I crazy for being super pissed off and not wanting to feel like a rebound in the middle of whatever they might have going on, or am I letting my insecurities get the best of me and someone I’ve grown to almost L word? Please help://