Is it possible for one to experience both in first week? Is my stomach going crazy?
Constipation or Diarrhoea for Keto beginners
Sure. Carb withdrawal affects different folks differently. Keep up your electrolytes, especially sodium, and it will pass. Welcome aboard!
For me those two problems are related to salt intake. Not enough salt leads to constipation, too much to something that is very much the opposite. Potassium and magnesium are involved, as well, but it is much easier to keep them in balance if we are getting the right amount of sodium. Ignore the government recommendations; try for between 2 and 3 U.S. teaspoons of table salt (sodium chloride) a day, including the salt already present in your food.
Other symptoms of lack of sodium can include dizziness, light-headedness, and headache. I find that an extra pinch of salt is often enough to head off a migraine before the aura can even develop into a headache.
P.S.–You may also find that your digestion is somewhat better if your fat sources are mostly butter, lard, and bacon grease instead of vegetable oil.