Drinking water advice

I have a HUGE sweet tooth but I wanted to slow down on my sugar intake so I decided to stop drinking soda and I had done this before 3 yrs ago when I wanted to lose some weight and it helped so much! ( If you’re looking to lose a few pounds, drinking only water and some light exercise helped me lose 50lbs in 7 months ) so back to my question. I recently started to drink only water again and I have been going on strong for a month now and I was wondering if anyone who has experienced this as well or knows someone who has if you or they have felt sick, almost like you have no desire or energy to do anything. Like you’re drained from the time you wake up to the time you go to bed? The only reason I am asking is because I didn’t have these same symptoms when I first tried this and I know that if you decrease your sugar intake of course it’s normal to lose some energy but to have lost all of it and feel almost sick and other symptoms like nausea, fatigue, a build up of mucus? Is this normal?