Since many women don’t announce their pregnancy until after the first twelve weeks have passed uneventfully, you’re unlikely to be able to sleep at work, or to get any understanding for your tiredness.
The only way to deal with fatigue during the first trimester is to try to get more sleep. Go to bed earlier, and wake up as late as possible. Avoid doing anything overly taxing, and just focus on getting through the day.
What you eat can have a big impact too. Eat foods that are slow to release, and fill you up. Whole grains combined with protein are a good idea, so snack on muesli and yogurt or whole grain toast and cheese for breakfast, followed by a balanced lunch, and a healthy dinner.
Lastly, make sure you stay hydrated. Being dehydrated can make even non pregnant people tired, and it will only make your fatigue worse.