Your medical condition must be scary and difficult. I’m glad you are seeing a psychologist. I hope, I hope, I hope you are sharing with your doctor what you have shared with me. If not, please take your letter to your next appointment as a way to help him or her know how discouraged and lonely you are feeling.
It is possible that a family therapist could help you have a better relationship with your mother. Do consider talking with her about whether she would be willing to go to some sessions with you. Your bad relationship with her may be at least partly because she doesn’t know how to help you. Going to therapy together could help you both be better at communication and would perhaps give you some practical skills for supporting each other during this difficult time.
The best way to find friends is to join something. You do have a couple of friends. That tells me that you have what it takes to be a friend. If your medical issues make it difficult to participate in active activities, consider doing something like writing for a school newspaper or local newspaper or joining a video game group.
In the meantime, please think about joining one of the forums here at PsychCentral. People from all over the world give each other advice and support. Yes, you need local friends as well. But online friends can also help you feel more supported and less alone.
I wish you well.