Insomnia Support Group
Insomnia is a symptom, rather than a disease, and is characterized by inadequate quantity or quality of sleep. People with insomnia complain of difficulty falling or staying asleep, which results in significant impairment of daytime functioning. Insomnia is categorized as transient (shorter than one week), short-term (one to three weeks) or chronic (longer than three...
So one can feel dead tired but unable to sleep. That's what late night caffeine does to me. It's awful. I want to sleep but can't. When that happens, I just accept rest and know that my sleep drive will be that much stronger the following night.
Sleepy to me would be similar to drowsy. It is a physical and mental state of lacking energy, focus, and needing rest that is experienced prior to sleep.
For most people, there are obvious signs of sleepy and/or drowsy. They include such behaviors as dropping eyelids, involuntary head nodding, and yawning.
Normally, most people have some sort of transition state between full wakefulness and sleep that includes a sleepy/drowsy phase. Different people would experience this in different ways.
Very few people go from completely awake to fast asleep without at least some transition. One possible exception might be those with narcolepsy, but generally those with that condition describe feeling feel very tired or sleep deprived most of their waking hours even after sleeping.
Have you looked at factors like diet and/or prescription drugs that might be causing you to not feel tired or sleepy? Have you brought this to the attention of your doctor?