So all these problems started at the same time about a week ago.
'91 s10 Blazer

-Driver side tail light doesn't work at all (turn signal, tail light, brake light, etc.)
-When I press the brakes all my marker lights and my instrument lights turn on.
-When my headlights are off and I turn on my right turn signal, all my marker lights blink (as if my hazards were on)
-When my headlights are on and I turn on my right turn signal, the light comes on but doesn't blink.
-Interior lights keep blowing fuses (not sure if related)

I don't even know where to start...

 

You should have just added this to your other thread you started, instead of making a new post.

as for your tail lights and exterior lights doing weird things, did you happen to replace a bulb recently on the side that does not work?

 

No. The only thing that had been done recently is I welded on a roll pan. I cut off the plug where you would plug in a trailer... would that affect it?

 

Did you seal the ends of the wires you cut or just leave the ends bare?

 

That is where I would start than, Sounds like something is shorting out back there since you cut the plug off.