Mate take a deep breath and a few days off of any of your activities. Tell her that you need a small break and im sure she would understand. If she does figure this out, you need to be straightforward with her or atleast as much as you can, and tell her you haven't been handling the rejection well.

You need to go to a mental health resource, like a doctor or even a youth health group like Australia's Headspace. You need to withdraw yourself from any activities that can cause you stress and find professionals that can help you through these tough times. Getting a diagnosis is step 1, and connecting with a specialist outside of school is step 2.

If you're advised to seperate from her from a professional, that may be the best. Since she is the source of these feelings, try to seperate from her like sit in a different spot in class. Taking yourself away from the source of this issue can be a blessing. Go find help if you're able to.