"I feel this empty lonely, sense of despair, and there is no reasoning behind it."

Don't get too hung up on that because there is a reason. An illness is an illness. It's like asking a pancreas of a type 1 diabetic why it's being such a ****. It just is and you have to accept that and treat it.
I'm sorry you're feeling this way and don't have anyone you can really talk to about this in your daily life. All of us here seem to have that common thread. I know others here and I will be more than happy to hear you out and help as much as we're capable.