Nikon d3100 factory settings?

I have a Nikon d3100 and all the photos take on it are blurry. When i originally bought it was working fine and with all the lenses, but now whatever i do they are still blurry. I think i might of bene me messing about with a setting, but i don't know which one or how i did it. I tried re-setting the factory settings thinking it would work and get it back to how it was, but i have obviously done something that isn't changing back! WHAT DO I DO? I really need my camera working properly again.

I usually use 18-55 lens.

Put the camera in auto mode, go out on a bright sunny day, make sure the autofocus switch on the lens is on A (auto), and take a few photos of something 20ft away.

If the photos are OK, then your camera is OK - which means you setup something that does not match the scene you are trying to photograph.

If the photos are still blurry, then it may be a problem with the camera.

The fault is more possibly you, are you holding the camera properly? Are your shutter speeds set to low?