Nikon D3100 shutter sound afftects my pictures?

I really don't know much about photography yet, my class starts in November and I just got the D3100.

his past weekend I was taking photos just fine, several of them in fact. I went to take more photos a few days later and after 2 or 3 the shutter sounded like it was taking an eternity and I was getting overexposed photos. Severly overexposed photos. I would leave the camera on a tripod in bright sunlight and still couldn't take a picture of a fence without it looking like a white blob. I've tried changing settings including my ISO (because that's the only thing I changed from the weekend until then). My battery was running a bit low so I tried recharging it, that didn't fix anything. I reformated the memory card and that didn't work. I cleaned my lens, that didn't work. I tried resetting factory settings, that didn't work. Is there anything else I can try? Is there a flaw with my camera?

Added (1). I do not have the focus at Auto. I'll try reading over the manual. I think it may have been a wrong setting as I was setting it up when I first got it, and I want to reset the camera to factory settings. Do you know how to?

If you would take the time to read the instructions that came with your camera or any basic photography book you would know that you need to increase the shutter speed.

Do you have the mode knob set to M (manual) or S (shutter)? If so, you need to turn the little wheel on the right side to adjust the shutter speed. As to out of focus, do you have the switch on the left side of the lens set to M or A (auto focus)?

Manuals are wonderful things, although I find the Nikon one a bit confusing. Try reading it thoroughly.