tail lampfuse blows when ignition engadged

[shiftgrl]

1990 Buick Park Ave
Tail Lamp fuse blows and takes the drive lamps with it when I turn the ignition on and engage the switch. Have changed the fuse 100 time and fuse blows everytime I start the car. But the fuse is fine and all the lamps work until the ignition is engaged. This is a huge problem for driving at night with no rear lamps. Head lightsare on another fuse. can some one help me figure this out. I'm stumped. Ive checked the wires at the back of the fuse box and at all the wiring harness they seem fine.
help help help!!!!!!!!!!!!!!!!!!!

Oh and my honey pop the question last night with a fat ring! Feels funny to wear it when I'm pooking around under the hood