I have every assurance that you are smart. You are just overwhelmed. I know the feeling. I felt it a lot as an undergrad and I'm sure I'll feel it again if I ever get into grad school (fingers crossed). EVERYBODY gets stressed around finals. And people with mental illness get it 10x worse. So remember to take breaks (I'm having to remind myself of that right now), take things one step at a time, break things into small chunks that you can achieve in a reasonable amount of time and keep plugging away. If after all that it doesn't end up working out, you'll have some time to regroup before August and you'll be able to get a fresh start. It's not the end of the world, even though I know it feels like it. You can do this.