2001 Honda Civic Smell Gas Around Back Half Car Time Even S Been Parked Over

I smell gas around the back half of the car all the time even when it's been parked over night. I could use all the help and pictures I can get. I can't afford to take it to a shop. There's no check engine light on. All the spark plugs are fine. No gas on the ground. Gas cap is tight and makes a vacuum sound when you open it after you have been driving for a bit.