CosmicRose wasn't trying to belittle your feelings. It's true that people often have rich inner dialogue, more than you probably imagine. This is key. It's absolutely imperative that you begin to imagine people more complexly because that will help you when you begin to dwell on things.

The problem you're having is one I'm acutely familiar with. I too obsessed over the littlest things in my life when I was young. I still do to some extent, but it generally takes something more serious than the minutia of daily life. As a writer, I live in my head all day every day, and it's sometimes not even about things that are real. I actually think that being creative, and spending time thinking about things that had nothing to do with me personally is what saved me from the vicious cycle you're going through. Distraction is a great thing.

It's important to talk to your therapist about this, and how much it impacts your daily life. If you don't learn the strategies to combat this now, it will get worse. When you begin to obsess, it's important that you catch yourself doing it. That's the first step. Everyone is different, but when I caught myself doing it, I would think something like, "Okay, my brain is going to do this whether I want it to or not, but I realize that, from this point on, whatever my brain throws at me about this subject is skewed and probably making more out of the situation than is actually there." I would also try to write things down before I began to obsess over them, so that I had an account of what actually happened before my brain made it bigger or worse than it was. Again, everyone is different, but you can work with your therapist to figure out what strategies work for you and your brain.