ok im at my wits end here i have a 2000 f-150 4x4 5.4L, under the drivers dash there is the fuse and relay block along with the 4x4 brain and a big black box all together, for the last year or so different things in the cab wont work and then ill hit it or kick it and stuff will start working again, its been getting worse and now radio,windows, and 4x4 and other things arent working, ive taken it out and checked for loose wires or plugs but didnt find anything, is this box bad and if so where can i get one

PLEASE HELP!