You are a human being, so you are always of value. You are at uni, you are doing something with your life and in time, will meet amazing people.
Think of it as they way, no matter how many times a £20 note is stamped on, it still has value!
I'm very sure you have a lot of fantastic qualities to give.
See you doctor with the chronic pain and Hopefully1 above has given great advice.
To help with friendships:
1) Relax, imagine you're just observing or there as a traveller. For example, if you are on holiday, you go there to experience and observe the attraction, you're not going to get anxious doing that are you?
2) Smile, smiling in contagious.
3) Be confident, respect yourself, accept yourself, work out, wear good clothes, feel good, focus on your passions, know you are a good person who treats people well, think positively, be proud of yourself, do things that make you happy, remember your happy times, what makes you confident?
4) Dress well, have good grooming, hairstyle, have good posture.
5) Just say hi or hey to people in your vicinity, who cares if they don't say anything back?
6) Ask how they are, how's everything, what made them choose this course, their plans for the future, their plans for the rest of the day, weekend, how was their weekend, what they will get up to, ask them about their hobbies, talk about the weather or did you see that sports game?
7) Be passionate about life.
8) Lighten up, have a laugh, laugh easily, be friendly, approachable, interested, relaxed.
9) Look outside!
Good luck!