A splash of milk or cream in your coffee or tea is OK, but beware that the carbs can add up if you drink multiple cups in a day (and definitely avoid caffe lattes!). For a more accurate way of determining ketosis, people can check the levels of ketones in their blood, breath, or urine. People in ketosis may experience a variety of side effects and symptoms, including headaches, stomach upset, and changes to their sleep and energy levels.
Avoid sweeteners that raise blood sugar, cause insulin spikes, stimulate your appetite and kick you out of ketosis. Apart from the obvious limitation of net carb content in foods, it is also recommended to avoid processed food and any food that may contain preservatives and colourings. Slowing down doesn't mean the new diet stopped working; it only means your body is re-adjusting itself to accommodate the new diet. Weight loss, or more like shedding the unnecessary extra weight, is only a side effect of a new, healthier lifestyle, which will benefit you on a long run, not only short term. Obviously, if you find yourself feeling fatigued and weak, consider that keto may not be for you, or at least look again at how you're trying to follow a keto diet.