My Nikon D3100 won't focus correctly anymore?

I got my camera in September, I have never dropped it and I take good care of it, recently I've noticed if I try to focus up close it will not auto-focus correctly and will not take the picture, what should I do? YES I did read the manual…

There are reasons why ANY camera will not auto-focus

* If the scene is too dark for the auto-focus to operate properly. The auto-focus assist lamp should be turned on.
* If you are attempting to focus closer than the minimum focusing distance, the lens will not focus closer.
* Your 18-55 mm lens can't focus closer than 0.9 ft. (0.28m)
* If you want to focus closer, you need a macro lens like the AF-S 60 mm f/2.8 macro

You might be on Manual focus? Try switching it to Auto Focus. Hope this helped

There are typically three reasons a DSLR will not autofocus.

1. You are too close for the lens to focus properly.
-- All lenses have a limit as to how close they can focus.

2. There's not enough light for the autofocus system to properly work.
-- DSLRs have an autofocus assist lamp that can be turned on or off to help in this regard.

3. The Autofocus/Manual focus is in the manual position.
-- Nikon lenses have a M/A - M switch. M/A=autofocus/manual override, M=manual.