Question about my gas tank door opening all the time & now clicking?

What is your question?

I have a nice Cadillac 2000 Seville, recently the gas tank door has been opening on its own & now it clicks all the time(coming from that area) thinking it's probably a sensor but have no idea how to fix it, just wondering if anyone knows or has ever had this problem, before I have to put her in the shop? Thanks