Based on what you have written in your letter, you are experiencing psychiatric symptoms that are troubling to you. You mentioned that now and in the past you have had anxiety attacks, insomnia, depression, mood swings, cutting, irritability, and much more. On the basis of this short letter I do not know if these symptoms mean that you have a borderline personality disorder but what is clear is that you are in distress. Because of this and until you no longer experience symptoms of a stressful nature it would be helpful for you to be in treatment.
You have been in treatment before but you said you’d stopped. It is important that you do not stop until you feel completely better, or at least until you have made significant gains. If you never follow through with treatment, you will likely have to continually battle the aforementioned symptoms.
As for your psychiatrist, I do not know if you should stay in treatment with him or her. Only you know best if he or she is helping you. Generally psychiatrists do not engage in talk therapy as a form of treatment and usually are only concerned about finding the correct medication to treat your symptoms.
If this is the case for you, you might want to expand the type of treatment you are receiving and start therapy. In therapy, you can explore what might be causing your depression, anxiety and mood swings. A good therapist can help you understand the nature of these symptoms and work with you to find ways to decrease their intensity and frequency. In using medication alone as your only form of treatment, and by not engaging in therapy you risk masking your symptoms and never really knowing what is at the root of your continuous depression and anxiety.
Regarding your friends and family, it’s probably best not to go to them for a mental health diagnosis. For issues regarding your diagnosis, a therapist or your psychiatrist is best equipped to answer these questions. You can and should, however, go to your friends and family for encouragement and support. Take care.