Nikon D90 Continuous Shooting?

Does the nikon D90 have to be in sports mode only to be able to do continuous shooting. Because mine won't work in any other mode besides that. Is there anyway to shoot continuously in auto or portrait mode?

The D90's pre-set modes aren't actually meant to be used, Nikon only puts them there so they have something to fill the dial with. A relatively nice DSLR like the D90 needs to be used in one of the user controlled modes. There, you can choose continuous shooting, your metering choice, ISO, shutter speed, aperture, white balance, and so on. Long story short, learn to use the M, P, Av, or Tv modes.

Just make sure you have continuous shooting on instead of single picture

Why on earth would you want continuous shooting when photographing portraits? It's meant to be used for fast moving subjects (wildlife & sports) not stationary subjects.

Continuous shooting should work in at least P, S, A, & M modes.

See page 64 and 65 in your manual.
As a previous poster said, don't use the idiot modes (sports, baby, disco, … ). They are put there for marketing purposes and lure the point & shoot crowds with excess money.

Don't use this camera in Auto mode! Use Program mode which is the same as Auto, but you control when the flash pops up and you can adjust the exposure compensation control (page 90 in your manual). This suggestion is true for all DSLR cameras.