You have left and right handed threads. It looks like this inside the arm //////// and \\\\\\\\
Now you're run both pedals in the wrong way, so you have threads that look like this inside the arms XXXXX* and XXXXX*
That's gotta tear up a lot of soft aluminum and weaken the pedal attachment.
*This is just an artist's representation. What's going on inside your crank arm is probably all screwed up even worse.