Life, love, and marriage

My wife and I have been on rocky ground for quite some time. More particularly, things have been pretty rough for the past four years. I've tried and I've worked at it, but I cannot seem to make her happy.

She's done a number of questionable things during this time, and I'm finally worn out. As of now, I am sleeping in a separate room and cannot stand to be near her. It hurts too much to know that the person that should love me and cherish me can't even talk to me on the phone after a couple of weeks of not seeing each other.

So - my question is this:

What in the world is the purpose of marriage?

I've found it to be lonely, demanding, hurtful, depressing, and difficult. It's reinforced everything bad I've ever thought of myself and has brought out the very worst in me.

Life sucks.

-Bart