My tail lights dont work when i turn my head lights on?

Well sounds like you probably fried the switch, i'd try replacing that if it doesn't solve your problem, be prepared to start tracing wires. Start from the affected area and trace it all the way back. You could have melted a wire which is causing it to short out or you could, have killed a relay as well. Did you just check the fuses under the dash, because there is probably another fuse box under the hood as well where you can check some of the relays.