Had this happen on a car a couple years back. I bought lots of spare fuses and a variety of new bulbs. I removed the bulbs one at a time to see if the fuse stopped blowing. Don't forget lights on shift indicators if there is a console as well as dash lights. I even disconnected the dash harness and radio. Disconnect as many items on this circuit - light, radio, etc to see if the fuse blowing stops.
I eventually had all the bulbs removed and as many connectors disconnected on the headlight circuit that I could find except the licence plate lights so started taking the lift-gate apart to access the bulbs and discovered that the rubber conduit between the body and the lift-gate had shorted wires inside of it. I repaired this and all was fine. So, obviously take a close look at the wires inside the conduit at the doors, tailgate, etc as it's a weak link due to movement and chafing.
Also, google this problem and your vehicle type and see what others are complaining about. This will give you some ideas and identify common electrical failures.
