Taillight Problem...Please HELP!

[Longhorn Al]

Let's see if I can explain this at all. haha

I don't know what it is called. When I bought my truck it had a trailor brake system installed (no idea what they are called). It has the little box deal mounted under the dash on the left. Push on the brakes, lever moves to the right and little red light comes on.

Ok, recently, when I turned on my head lights, the headlights would come on. But the taillights, rear side markers and dash lights would not. Flashers and blinkers worked. Not sure about the brakes.

My dad and I messed around with it and replaced a fuse. Everything started working again. Two days later (now), the problem is back, but with a strange twist:

I have my headlights on (taillights and dash don't work obviously). Now when I brake, and push that little lever on the box over manually, all my lights come on. I can only do this while stepping on my brake. When I step on the gas, the lights go out. And they only come on when I manually pull that lever over (and it's pretty tough to do).

Also, my back up lights have never worked properly. One is out and the other blinks. But that is another problem that is not as important.

Please HELP ME!!! Thanks.