Would you consider this cheating?

So my fiancé and I have been together for almost 9 years. We have three children. I have been struggling so badly with ppd and ppa since our last

baby was born. I spent a month and a half in the hospital and then had him 6 weeks early and then he was in the NICU for a month and a half. I have been struggling since. He has not been supportive or there for me at all. I have been having a feeling he was lying to me about where he was going when he says he’s out with his friend. Today he left his phone charging and I know I shouldn’t have but I looked and I found this 😔. I saw him talking to a girl a few months ago and he swore he deleted instagram. I found it in a folder hidden. I want to leave. I’ve been a stay at home mom for 6 years now. I dont even know how to go about leaving. I just don’t know what to do. I’m so beyond hurt. The message where he says the kids are with their aunt. They were with me and we were visiting family. I doubt this girl even knows I exist or I’m in the picture at all. Based off his instagram he looks like a single dad.

I am really struggling with this. My depression has been so bad lately I am now questioning if maybe they would just be better off without me. I don’t know what the point of this was. I guess I just needed to vent and put my thoughts somewhere. If you made it this far, thanks for reading.