Sounds like you need a setup.....most music stores offer this service. A setup includes adjusting the truss rod (leave this adjustment to someone who is experienced, the neck can be easily broken by someone with no experience.) They may also adjust the bridge saddle heights and intonation.

Keep this in mind.....Climate has a big effect on a guitar. I do a setup on my guitars at least twice a year (winter and summer). Also, changing string gauges or changing tunings from say standard tuning to 1 step down will also bring on the need for a setup. All of this is because a guitar is made of wood, and wood will shrink and swell, so adjustments have to be made to accomodate for this.