Filling up with fuel

For a few months I would get a warning light on the dash saying tighten gas cap. But that would come and go so I thought i was just not tightening the cap enough because it would go away. I have not seen this warning for a couple of weeks. Now when I try to fill up the gas tank the pump will start and within a few seconds the pump will stop when I try again it does the same thing making it impossible to put gas in the vehicle. Now I am wondering if this new problem is related.