Reading your post was like reading pages from my own life. My entire family (which denies the very existence of mental illness for the most part)has cut me off. Mostly through therapy, I have come to understand that not everyone (even family or close friends) can cope with the daily roller coaster that we bipolars endure and often create. It can be extremely draining beyond what many people can actually handle and they find that they must distance themselves, even when we may need them most. Truly, they are distancing themselves not because they don't care about us, but because they too have to look out for number one. Just like we try to look out for our number one by reaching out for help. Even loved ones who are well-educated about our illness can experience this. really understanding this about others helped me a lot. that does not mean that it does not hurt, but it does mean that it is not about not loving or not caring.
To cope, I reached out to people who were bipolar too. There can be strength and understanding in numbers. We are each others support. Most of these friends of mine are online. I found them at places for bipolars, mostly forums and some chat. In 'real life', it is a bit harder to find like minded people. You might want to try a local support group or possibly one online.
I truly sympathize with your experience and wish you the best. Any time you want to talk, i would be happy too.
Take care.