When I taught college I had a number of students like you. Often they weren't in any danger of failing - and it doesn't sound like you are - but they just couldn't get past thinking and worrying about their grades. So this is quite normal.

Can you sort of recalibrate your thinking? Did you enjoy your courses (for the material, not for the professor or fellow students)? Did you learn anything? What was it? Was there anything especially interesting or enjoyable in the courses that really attracted you? If any of the answers are yes, try to focus on that. Learning brings lifelong enjoyment; grades bring only stress and maybe a momentary victory. And if you did learn something that intrigued you, or deepened your knowledge of the world, does the grade really matter?