What you describe I definitely relate to...

I think you should talk to you psychiatrist or doctor and tell them about the difficulties in your relationship and also your fluctuations in mood and fear of abandonment.
It's their job to explore that and diagnose..

It's difficult because anyone can read a page on BPD and feel they relate but that's it's the intensity of these symptoms that make the difference.

Even If it isnt BPD, you need help as you are clearly facing a lot of difficulties and maybe some of the treatments used for Bpd will help.

Keep us posted