Hello. I don't understand why you would denigrate yourself. You ARE smart...clearly. If I may offer some friendly advice. It's very easy to be overwhelmed senior year. That said, I have been there, done that, and it doesn't all have to be done straight away. It's perfectly fine to take time off from anything. You need to know that. Nobody will think less of you for taking care of your health first. And that is my next piece of advice. Prioritize. Break all of these things down. What can be put off? Can you talk to your teachers or guidance counselor? Can you make up some work or squeak by with less than an A? Is summer school an option?
Will you be better going to college in September or taking a year off? There are pros and cons to both. Pros are that you will get more support there, cons being that you will need it.
It sounds as if you're overwhelmed. Personally, when it gets to me, I go all crazy organized. It helps me feel in control. And, of course, reaching out is always good.
I'm happy to talk at any time.