Whats the best way to manage stress at work. left today with a bad headache.

You are smart: to want to get a handle on this. It sounds like you have already begun to identify what triggers stress--some conditions at work. Often simple things add: commuting, balancing home/work, etc. Focus on eliminating the triggers first. Then the lifestyle basics: healthy eating, exercise, sleep. From there I advise Mindfulness Meditation, deep breathing, Yoga, massage. Read up on these. Best wishes:)