The on and off pigmentation seems to be stress related because of your hectic work schedule. A good sunscreen with SPF 25+ gel form,(since you are prone to pimples) during day time and a night cream containing kojic acid should help you. Also add some fresh fruits and green leafy vegetables in your diet. As far as chapped lips are concerned,you should use a good lip balm as and when required.
Next Steps
visit a skin clinic. get some in office treatments like chemical peel and/or q switch laser. your Dermatologist might prescribe you some anti oxidants and supplements after examining your skin.
Health Tips
don't buy over the counter whitening cream, they might help you initially but may be harmful in a long run.