The reason you cannot sleep may be an evening coffee. How long caffeine actually stays in your body.
Caffeine does not restore energy. It occupies the place where the sleepiness signal would normally land, so you stop noticing the signal. The signal itself keeps building up and returns all at once as the caffeine clears. That is why an afternoon coffee can be followed by a sudden collapse in the evening.
Caffeine takes roughly five hours to fall by half. A cup at three in the afternoon is still half present at eight in the evening and about a quarter at midnight. If you fall asleep but wake repeatedly or sleep lightly, moving your last cup earlier usually helps faster than cutting the amount.
Counting only coffee misses your real intake. Green tea, black tea, cola, energy drinks, chocolate, and some headache and cold medicines all contain caffeine. Small amounts through the day often add up to two or three cups of coffee.
Daily use reduces the alertness you feel from the same amount. Stopping abruptly from there can bring a headache and sluggishness for a day or two. That is not damage, it is the adapted state unwinding. If you plan to cut down, reducing over several days is more comfortable than stopping at once.
A racing heart, shaky hands, anxiety, or trouble falling asleep mean the current amount is past your own limit. During pregnancy, or with heart or stomach conditions, the sensible ceiling is far below the general one, so check with whoever is treating you rather than deciding alone.
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