My mom found a Pride flag in my room. I can tell because it was moved in the drawer where I keep it. I'm pretty sure it was her but I don't know. I'm not ready to come out but I feel like she knows now. What should I do?
OK. deep breaths.
Here's the thing: if she did find it and hasn't said anything, you're probably fine. Now, I don't know her so anything I'm saying here is pure speculation.
But, look at it this way: if it's something that was problematic and sent her over the edge, you probably would've heard about it immediately. You would've been confronted, you would've been challenged, you would've been emotionally destroyed, you would've been verbally beaten.
Instead, maybe you did just "come out" in the easiest way possible: without having to say a word.
I don't have kids but my brothers do. I had a chat with one of them a few years ago. We talked about the idea of one of his kids possibly "coming out" at some point (neither has, it was just something that we discussed). He said if he did find something (gay websites visited on the computer, texts on the kid's phone, etc.) that he'd make note in his mind and file it away for when his son is ready to address it. No biggie. As a parent, he'd prepare himself and has time to respond appropriately.
If "not being ready" means preparing yourself for the conversation and how to approach it then maybe it's a good thing she found out this way. Maybe she's not saying anything so you don't feel uncomfortable. This could also be one of those situations where you both know you know and there's no need to say anything until the time is right. That's not a bad thing.
Besides, it's just a flag. If it was harmful drugs or hardcore porn, then I'd say you should be crapping your pants in fear. It's a flag. She hasn't made a big deal about it, neither should you. If she's the one who discovered it, it's on her to communicate whatever she's feeling. (Maybe she didn't notice it, maybe it wasn't even her.)
As for you taking the step to officially "come out": well, that's a decision every person has to make at their own pace, at their own time. If you feel like you need to ASAP because of the flag thing, remember, you might be forcing yourself into discomfort when there's no need to.