Possible Electrical Short?

This evening I moved my trailer to a friends house. Before when I was towing, the park lights would come on when I used the brakes. I got used to it and had no problem. Tonight however, when I started up my truck, plugged in the lights, then hit the brakes, my left turn signal stayed on and never turned back off. Even when I tried to use the turn signal switch, it didnt flash, just stayed on. It does this with the brakes too now. With the headlights and park lights off, it turns off. As soon as I use the brakes, the park lights, dash lights, and turn signal turn on. Any ideas on what caused this and what I can do to fix the turn signal until I can buy a factory OEM tow harness? Am I going to find any of these oem tow harnesses lesser than $100? And where? I also thought I could smell some sort of hot wire, or burning insulation when I got out.