I imagine you would feel more tired if you were in hospital with a cancerous lung and have tubes stuck up your nose and an enema shoot sticking out of your bum due to a complete loss of bowel control. I have heard such things may cause an uncomfortable nights sleep.
So...................well done for stopping this foul and odious habit. After years of violently abusing your entire body, of course there will be side effects. These will go in time and only goodness will follow.
Forget healthy eating, a stress free life, caffeine, alcohol, a decent exercise regime and other things, the single best change of lifestyle to improve your overall health is to continue to stop smoking.
Carry on and may the future bring you a cancer and heart disease free life!!