Viewfinder on my D3100 is sorta blurry?

OKAY. I have a Nikon D3100 and it has the live-view feature which i don't use that much.
i bought my camera on March 1st, 2011 so its exactly 2 months old, basically new.
when i go to focus my subject i started to notice it was a little blurry but when i switched to the live-view on the LCD, in was perfectly in focus.

it looks like there's a smudge or something on the INSIDE of my camera. I already cleaned it well, and same thing.

NOTE: my eyes are getting a little worse (i wear glasses), and maybe that's why. But i'm not like getting blind.that's probably half the reason, but even other people using it asked why it was always blurry.
* also, i have never touched the inside of the body, (The mirrors and glass things, because i'm too scared ill mess something up) so it can't be a fingerprint

To me it kinda sounds like you need to reset your camera, so that everything goes back to the normal settings. I had problems with that as well on my Sony A230 and I rest my settings and it worked just fine. Also, if a little dust gets into the lens and body it can mess it up as well. Lived with both of those.

It could be as simple as adjusting the diopter adjustment. It should be a little slider or knob up right next to the viewfinder. Just tweak it a bit while looking through the view finder.

I'm not too familiar with the D3100, but I have a D90. On my camera there's a little knob to the right of the viewfinder that adjusts the viewfinder's focus. From the pictures on Nikon's site, it looks like the D3100 has the same thing. Try adjusting it and see if that fixes your problem.

Try live view - if it is not blurry then adjust the diopter until it is clear for you.

It's likely you've nudged the dioptre adjustment by accident (easily done).It's the small wheel right next to the viewfinder, with a +/- indicator. Its to adjust the 'crispness' of the viewfinder view for people with different optical prescriptions.