I've had bipolar about as long as an eating disorder, 17 1/2 years. Also GAD and OCD. It's hard, but you are not alone. It can get frustrating for sure, as the ED influences and is influenced by the other disorders. Hopefully you can find a good therapist with ED experience and expertise in mood disorders; same with a psychiatrist.
I wish I had solid advice to give you that would make everything easier, but I am with you- it can get lonely. The ED by itself is alienating; that's the nature of the disorder. Bipolar on top of it- the depressions make that loneliness seem everlasting and all-encompassing which just feeds the hopelessness. The manias, well mine tend to be mixed so it is like the depression is shining a black light on everything, electrifying every symptom ED or otherwise.
I guess I would say just remember the ED lies, and the bipolar can zap you of strength but hang on, you will get through. Remember all the things you hate about the ED and what it strips you of. Remember you are not your disorder, either. EDs are notorious for making you think you are nothing but that- disordered. And that can cause you to get caught in a cycle of negative behaviors being reinforced by the the mood disorder's faulty thought patterns.

I don't know if that was much help, but bottom line is you ARE NOT alone. You've at least got all of us that have replied.
Don't give up hope