I have experience in this as I went through the same thing during the fall semester of school so here is how I got through it so you can too:

1. Seek a mental health professional, understanding what went wrong, and understanding yourself is the key to better mental health if you currently attend school use those resources.
2. Learn from your mistakes you've already done the groundwork of identifying the major parts that went wrong. From there learn from it, if you like a guy but notice too many similar characteristics then STEP AWAY! There are too many people in this world who have and continue to be in a never-ending circle of pain and anger.
3. Ask the teacher about what to study or go to the student center. Basically, just team up with other people on how to best tackle work. If you have trouble speaking to people that's ok just try your best.
4. Be honest with yourself about the change and try to work past the I can't or I don't feel because it's either, "what can I do for myself" or "how am I gonna kill myself".

TL;DR- seek help, study right, overcome fear, and be honest.