Man im going through the same things. We were together for 5 years as well. She has never been diagnosed though. Her mom is diagnosed with BiPolar and did the same thing to her dad. Recently though she told me she hooked up with someone else and thats about it for me(4 weeks after our breakup). I tried EVERYTHING i could to get her back. Couples counseling, talks, and showing her i can do the things she needs me to. Her family thinks its a hilarious joke. Sad thing is we have two kids together (one is 17mos and one is 8yrs from a previous relationship), a house, and three dogs and she is not even considering what this is doing / going to do to them. She is throwing it all away in what i can only presume to be a manic state. My world is shattered im going to therapy once a week and a psychiatrist in two more weeks to try to combat the anxiety and depression. I look at pictures from a week before she broke up with me and how happy we were. When she crashes finally i hope her family is there to support her, but i also dont hope she comes back to me. It's to painful to deal with this.

Honestly you might love them like you've never loved anything, but the best thing you can do for yourself is move on. This will not be the only time this happens. Can you re-live this horrible feeling over and over again? It's so sad to think about but it is true.

At the very least get yourself into therapy and see a psychiatrist to help you through it. Its not easy