2000 dodge caravan gas leak

it leaks underneath the van right where the gas tank is located. Not sure about the rubber ring replacement, we thought the tank was leaking, got another one and put it on and after one week, it leaks again in the same spot. Sometimes it has trouble starting, and when i put any gas over 1/4 of a tank, you can see it dripping underneath the van. I’m very short on money and not sure what to do next.