Sakura,
I'm sorry to hear about how complicated your relationship has been for so long. I can understand why you're frustrated, as he doesn't seem to be very stable. Is he getting treatment? Seeing a therapist? Medications?

It is always within your right to walk away from any relationship. You don't even have to have a reason; if you aren't happy that's reason enough.

I'm thinking if you're still not ready to let go of the relationship, and you two are close enough distance wise, perhaps you could go to therapy together. I'm not honestly sure what they would do, but it could be helpful. You could also look into support groups for partners of those with serious mental illnesses (Check NAMI?).

My last note is about the missed phone call. Where I work, the hallway where our lockers are doesn't get any reception. The rest of the building is fine, but I leave my purse in my locker with my phone in it. If someone calls my phone while it's there and doesn't leave a message, I will never be notified of a miss call. My phone doesn't recognize it. I don't know if that's something that could have happened to you, but it is possible.

Take care!