It's quite common for people who are sat using a computer all day to have imbalances brought on by bad posture. The usual problems are a combination of tight chest muscles and weak muscles in the upper back, caused by hunching over a keyboard all day, and tight hip flexors and glutes that are weak and inhibited caused by leaning forward in a seated position.

Hold a pencil in each hand and drop your arms so they're by your sides. The pencils should point straight forward but the problems noted above will cause the pencils to point inwards. If you strengthen your upper back (face pulls, reverse press ups etc) and stretch the muscles in your chest you should be able to resolve this.

If you strip to your pants and look at yourself side on in a mirror, the waist of your pants should be fairly level. If the front is lower than the back then you probably have a pelvic tilt that needs correcting. Strengthing the glutes (swiss ball legs rolls, bridges etc) and stretching the hip flexors should help.