light bulbs keep going out

I am hoping that someone can help me figure out what my problem might be and how to solve it. Last summer I had a new light fixture installed outside my main entry door. The past month or so I have replaced the light bulb about 5 times. The new bulbs are lasting anywhere from a day or so, to a week or so. Does anyone have any idea what might be happening and what needs to be done? Thank you all in advance.

Ruby