You would have to post a sample of your daily meal plan… What is the fat content of your diet? Try eating vegan then slowly add some healthy proteins back in.
Carbs will only be a factor if its sugar, if you are cutting carbs out then you will have no energy until you enter ketosis then your energy will rebound. Ketosis should take you 3-5 days to get to if you are eating less than 50 g of carbs per day. If you eat any sugar at all you stop the process of entering ketosis and will crash worse.
Are you on a particular low carb diet, and if so why?