Before doing anything drastic, check all the screws around your door frame and the screws on the door hinges themselves to make sure they are tight. If they have wiggled loose, the door is not seating correctly when shut, making everything on the door out of align, especially the door handle and catch. Go around and re-tighten every screw (or bolt) you can find associated with the door frame and the door hinges and see if that helps. That's the very first and the very least evasive thing you should do.
The latch itself should have 4 to 6 screws holding the inside and the outside together. They need to be tightened too.