You could be a codie ...
... or in other words, and enabler. You sound like you're the "compassionate ear" and the shoulder others with messed-up lives can rely on to listen to them, try to "fix" them, help them out, etc. It also sounds as if your darn sick and tired of doing it! EVERYONE has issues - that goes with life. But I know what you mean - some folks continue to wallow in their issues for years without doing anything constructive on their own about it. It's almost as if they gain their identity from their misery and bitching about the other person who's done them wrong. I have cut my ties with those folks. Now I mostly hang out with Al-Anon's or codies working a program. We take responsibility for ourselves, respect one another, and learn to accept and enjoy life on life's terms. Easier said than done ...
Were there any addicts in your family when you were growing up? Frequently someone with an alcoholic parent becomes an enabler to other people because they're so used to coping with the chaos of living in an alcoholic home. I'm only conjecturing here, so correct me if I'm wrong.
Don't feel guilty about screening your calls. After all, you can only listen to someone bellyache about the same old problem so many times!