Tail light and left blinker not working

If it was a short then the fuse would blow. It could be a damaged wire or corrosion in the light bulb socket.

It's weird though, It will work for 2-3 months then randomly go out, for a week or so then start working for a month or two at a time again. Its not the first time this has happened.

check the plastic wrap on the wire harness that feeds the light and look for a crease. remove plastic wrap to a point below crease. solved this problem on both my 2000 and 2005 f250s after changing left rear brake light several times.

forgot to mention you should see crease within 12 inches of wire harness from light