I accidentally overheard my parents fighting and found out some things I really wish I hadn't

I came home from practice early last week and could hear my parents fighting before I even opened the door. I've heard them argue before but nothing like this. I stood in the hallway frozen and then I heard my name come up. My dad said he'd stayed this long because of me and my sister. That he'd been unhappy for years. My mom told him if that was true he should have left a long time ago instead of making everyone miserable. I went upstairs and closed my door. They didn't know I was home. Two hours later they came down to dinner acting completely normal. My dad asked about practice. My mom made pasta. I sat there knowing everything I'd just heard and had no idea what to do with any of it. I started thinking about what was actually bothering me most. Part of it was what I heard. But a bigger part was the fact that they came downstairs and acted like nothing happened. Like everything was fine. I'd been carrying this thing alone for days and they had no idea. I also thought about whether I was supposed to say something or just pretend I didn't know, and whether pretending was something I could actually pull off long term. I realized that sitting on it and saying nothing wasn't really an option. Not because I needed to confront anyone but because carrying something that heavy completely alone was already affecting how I was showing up at home every day. I needed to at least tell someone what I heard so it wasn't just living in my head by itself. Talking it through helped me figure out that I didn't need to make it a big confrontation or force my parents to have a conversation they weren't ready for. We agreed the best next step was to tell one person I trusted outside the house what I'd heard. Just to get it out of my head and have someone else know. After that I could figure out whether I wanted to say anything to my parents at all. I wasn't ready to do that yet and I didn't have to be.