Other people are addicted to shopping, gambling, etc... I'm addicted to donating! Is this a problem.?

I'm sort of a compulsive philanthropist. I not rich by any means (teachers don't make past 5 figs), but I feel an overwhelming need to donate money when I see a worthy cause, and get a similar high level of satisfaction after doing it. Sometimes, I spend almost all of my free money (that I haven't set aside for savings) on donations to PlA, Kiva, etc... I'm not trolling - I'm legitimately wondering if I should be concerned, or if this is 'relatively' normal behavior.