Do I need to obtain a business License to be a portrait and wedding photographer?

I bought my first SLR over a year ago and have been bombarded with requests from people in my area to take portraits and shoot weddings. Countless portrait sessions and 5 weddings later, I am wondering if what I am doing is legal. I am getting paid, even though it isn't much. I would like to make a career out of this, but I want to do it the right way! Help please?