A paper in Psychopharmacology reviews studies of caffeine withdrawal symptoms and concludes that these symptoms "meet the bar" for being clinically proven withdrawal symptoms:
headache, fatigue, decreased energy/activeness, decreased alertness, drowsiness, decreased contentedness, depressed mood, difficulty concentrating, irritability, and foggy/not clearheaded
It lists some others that might be withdrawal symptoms as well, and points out
the incidence of headache was 50% and the incidence of clinically significant distress or functional impairment was 13%. Typically, onset of symptoms occurred 12-24 h after abstinence, with peak intensity at 20-51 h, and for a duration of 2-9 days.
If you really want to stop using caffeine, do so, knowing that the first few days will be the hardest and then it will get easier. By a week without it, you should be generally past the symptoms.
Since some of the drowsiness is actually just a withdrawal symptom, you may find after a week that you don't need a replacement (natural alternative.) Or you may find that you need more sleep, or to eat earlier in the day. Figure out what to replace it with once you are not feeling those withdrawal symptoms any more.