I have had patients with similar symptoms that have consulted many doctors and had several medical examinations without finding a cause of their problems. Eventually they ended up in my consultation where we worked with their inner feelings.
These patients have been suffering due to repressed psychological pain. During our work, strong feelings of anger and sorrow were recognized and expressed. After treatment, the patients' physical symptoms disappeared.
I am not sure if this is the case for you but it cannot be ruled out. Did you grieve your friend and lost love? Did you allow yourself to get in touch with your rage over your loss?
You decribe your losses as if they just struck you, as if you had no part in what happened. If that is how you conceive it, you may well be overlooking your own role in these events. Perhaps you are avoiding painful self-examination, and thus not learning how to deal with intimate relations so that, in the future, people will not abandon you.