You should Ben Franklin this situation, and my dear it is indeed a fiasco to say the least.  You need some clarity, you seem muddled and befuddled and too close to the forest to see the trees.

Take a piece of paper.  Put a line down the middle.  On one side write down all the Positive aspects of your relationship????  One the other side put down the Negative aspects.  Those things that have happened during all this time that make you unhappy, confused.  Then compare them. 

If the good outweighs the bad then you are on the right path.  If you find the bad is overwelming and you have spent more time unhappy and confused than happy, well it is time to say goodbye.

Life is long, there is a world of people, good, bad and ugly.  Go for the good.  It will sit well.

Do the right thing.