I'm not sure fear of abandonment is a symptom of Borderline Personality Disorder. But regardless it is your demon to deal with. Perhaps these 'friendships' of yours are not on your terms and hence quite toxic.

The obvious andwer is to make new aquaintanceships, but I realize this seems like an impossible task to do. Maybe start with listing off to yourself the qualities you DO want in a friend before searching them out. Make a list next of where you are most likely to find such people. I just recently started a walking and yoga program and have met some potential aquaintanceships. I have several from my support group too. What I am saying is that it is easier than you think to find potential friends.