I can understand where you are coming from! One year, I decided to give up Diet Coke (a big vice of mine; it is my “coffee” any day, all day!) I had a splitting headache for about five days! It sounds so melodramatic to say this, but I felt a shell of myself!

On a side note for you, “Hungry AND Tired” are a lethal combo!

It would be wise to get enough sleep!

I found that it helped not to dwell on it too much. You may consider reading Matthew 6:16-18 which talks about fasting and basically that we are not to put on a “Woe is me face” which summons others to say something such as, “You poor thing!” “You look terrible!” Or “Are you ok?” Our focus should remain on Christ; to unite our temporary suffering with His ultimate sacrifice for us. Praying for strength and to fast cheerfully may also help.
We have a young Transitional Deacon who will be ordained a priest this May. During a homily, he said that if we consistently make small sacrifices daily (saying no to a dessert, not having 2nd helpings, etc) it helps us to resist temptation more easily because we are in the habit of denying ourselves; temperance. For the first time, it made sense!

This may be little consolation for your growling tummy

, but I hope it helps a little.
I will pray for you!
Peace and all good!