First of all, I agree with the other commenters about getting assessed for a learning disability and/or ADHD. Your post is more coherent and well-written than a lot of stuff by people with degrees, and you were able to do the math to figure out if you were going to pass. If you aren't doing well in school, then it seems like there's something else going on there.
Second, you might want to check if there's a career center or something near you. If it turns out you do have a disability and you live in the US, there's a program called Vocational Rehabilitation (voc rehab for short) that can help with career assessments and such. If you're not US-based, other countries might have similar stuff; try searching for voc rehab or occupational therapy.
Third...you school only gives you seven hours to register for classes? That seems insane to me. Is that standard anywhere? Maybe your schools just suck, lol.
If you've got any Benadryl/diphenhydramine in your medicine cabinet, it has some anti-anxiety properties. Not really something you can take for too long, for obvious reasons, but it can help in a pinch.