Default [Q] i337 Overheats then no SIM

Its a 16gb Att and ive had it for about a year and few months. This started happening a while back but never this bad. I would feel the phone get really warm in my pocket. The heat comes from right under the Sim/SD card tray. CPU? So eventually i get so hot it gives me the invalid SIM/ no sim message and rebooting my phone fixed it. About a month ago i read here that it might be a corrupted or damaged SD card. And what do u know, i pull out the card and no more heat/ sim issues. I thought it was my card 64 GB Class 10 Sandisk. But no, every SD card i pop in that isnt empty starts this meltdown. So i had to replace the charger port so i swaped out that board, same issue. Replaced the SD/Sim card tray same issue. I put my finger on the piece the card tray sit on before i stuck on the new one (ribbon cable connected with SD card in slot) and almost burned my finger. I flipped on Dev options and checked off "show cpu ussage" and i see that everytime i pop an SD card in, my CPU usage goes NUTZ, like its low at idle then in shoots to 100% and stayes there for a little, then back down, then back to 100%.

Anyone know whats going on? Or how to fix this? Im out of warranty and the only way i can use my phone is to remove the SD card. And 16GB for me isnt enough.