Struggling with abandonment issues all my life, help?

Hello everyone.
I'm an only child of two hard-working doctors, which meant I have spent most of my childhood/teen years alone, craving their presence and attention. Add to it the fact that I had medical issues (surgeries when I was little) and lacked social experience due to being guarded at all times and not having a chance to interact with peers, leading to being severely bullied at middle school.
I have grown up since then, done a lot of work on myself to be who I am today - I studied psychology and now I work with victims of sexual assault. My work is rewarding and finally my empathy has a proper outlet and can be of actual help to someone. However, outside my stressful work where I am successful, my personal life is where my struggles lie.
I'm 34, never been married, heck I can't even remember when was my last real relationship.
I have a best friend - a girl my age which I knew since I was little but we reconnected about 6-7 years ago and since then we have become inseparable - more than best friends, it's like family.
We have been through thick and thin, using every free time to interact and constantly being in touch via facebook, whatsapp etc. even during work. She lives in another country, and we only get to see each other in person once a year, when she comes to visit her hometown, so online connection is all we have. It has never been a problem, however as much as I am an overly sensitive Cancer, who needs to feel that the deep care I give is reciprocated, she is a free spirited Gemini and often she tells me that I suffocate her.
I realize that my behavior when triggered is horrible - but I can't seem to help myself, no matter that I have explained it to her.
I would be balanced and normal for a long time, but then there would be a period of time, like the past few weeks, when due to work etc, time to interact will be sparse and severely limited, so that would make me feel on edge already. Then when you add that as little time there is, she would choose to spend it with other people -friendly colleagues etc, would trigger me and I would lash out at her accusing her of ditching me for those people, who aren't even that close to her, yet they get to have her time and attention, whereas she would chose to ignore me.
Yes,I realize I sound pathetic. And I need help to overcome that.
Especially it upsets me when she reacts in her defensive mechanism way - which is to retort in a way that confirms my fears - that I am not holding any special place in her life and that in fact any person who walks in from somewhere, could threaten that and easily take my place.
I have tried anti-anxiety medication, antidepressants, meditation, talking about it in counselling but nothing seems to help.
I notice that I get triggered the most when my life is already stressful, so when something like that happens, I feel like somebody is pulling the rug from underneath my feet and I am completely losing control and spinning.
I have not been diagnosed with BPD, however, this severe abandonment issue is present all my life and I really need help by at least talking to people who would understand how I feel, instead of in turn ditching me too and judging me for being "needy" and "possessive".
Sorry for my rambling text, I am usually much more coherent, but I have been crying all morning and I haven't had much sleep last night, so feeling at my rope's end here.
Any responses will be greatly appreciated.