My(18M) girlfriend(18F) of a few months is pulling away and I want to fix things

We had a great relationship going with no signs showing that it wasn't going to work out. She started messaging me less and less, but it still seemed like she was into the conversations we were having. I asked her if everything was alright bc she wasn't as talkative as usual, and she said all was good. She kept messaging even less and I asked her the same thing and she said everything was fine and to quit asking. I know something has got to be up with her, so I asked her one more time after a while, being a little more demanding for an answer, and she said we should take a break for a bit. I asked her why and she said she needed to "get her mental state up". We're still in high school and she has said before that she's very busy and gets very stressed, which I know is true and she's not just saying that. At this point I'm not sure if she really does just need a break and I'm just kinda being a jerk about it or if she's just trying to end things. I'm gonna try and talk to her about it and I wanna know how I can bring up the idea of trying to fix things without seeming bothersome or desperate?

Tldr: gf is pulling away and I'm not sure how to bring it up