2002 rodeo-tail light fuse shorts out

I replaced the 15A fuse twice and both times it burned out as soon as I turn on the light switch.I even tried a 20A fuse and it burnedout right away as well.I tried using a volt-meter to measure how many amps were coming out but was not getting nothing.Must be measuring incorrectly.Can anyone guide me on what to do next?Could the tail light wire be burned maybe?

If you have a trailer light connector give it a good look as far as condition and cleanliness.