On a health kick, doing a new 6 week challenge, a detox program, can't have alcohol, have to eat healthy, and drink lots of water etc. You could say it's a Belated New Years resolution??

TMI but depending on whoyou have to tell at work, you could say part of the detox diet makes you unwell as it cleasnes your system, so you have random days where you can't be at work due to vomitting/runs??
HTH

I tried a similar scenario when preg with DS, but they picked something was up with me at 6 weeks, I was running off to vomit every 5 mins! Dead giveaway for me in an office of girls!