I find melatonin very effective for the waking up at 4/5 AM problem, which is directly related to declining melatonin production as one ages. I use a sublingual form which is quicker acting. In me at least, no drowsiness in the morning, effects seem to pass altogether within 2-3 hours

Another thing to consider for those whose problem is waking up during the night, as opposed to (or in addition to) falling asleep to begin with, is the possibility of sleep apnea.

Toptuan, the OP specifically states that he feels very tired. So not a case of just needing less sleep. He also describes feeling very sleepy in the late afternoon but then alert at what should be bedtime, suggesting a problem with his internal "clock".

Tiffy is a cold remedy that contains an antihistamine as well as paracetamol and a decongestant. It is the antihistamine that causes drowsiness although that effect is in many people counterbalanced b the stimulant effect of the decongestant. If one is going to use an antihistamine for sleep I would suggest using just an antihistamine rather than a combo product that includes other drugs not needed.

OP, one other thought altho don't know if you can do much with it. From the way you describe your problem it is one of your internal bio-rhythm not being in sync with the times you need to go to bed and wake up. Everyone has their own internal rhythm and some people simply cannot really adjust to a very different schedule. My own natural rhythm is to go to sleep around midnight and waken around 9 AM. I have never been able, despite years of trying, to get well adjusted to an early to bed/early to rise routine unless it allows for a nap around noon, and even then not so well. At best I hobble through accumulating a sleep deficit which I make up for by sleeping late at the first opportunity. So I know what you mean. When I am able to follow my own natural schedule there is no problem at all, fall asleep naturally, wake up naturally, feel fine.

If it is at all possible for you to change your work schedule to one that better suits your natural rhythm that would be ideal. If not, what I did/do when forced by necessity to get up very early is to take Atarax once at the end of the workweek and catch up on my sleep. Not ideal but at least I then start out rested and accumulate just 5 days of insufficient sleep before catching up again.

i get 12 hours regularly and can sleep up to 25 hours if hung over is that wrong

I have been using melatonin successfully for the last 20 years and still have some bad bouts of insomnia..I play tennis everyday and go to the gym as well and although the excersize is great..it doesnt guarantee a good nights sleep. I also use the stillnox when needed and find that it gets me to sleep very well. People should be aware that it is a very addictive drug and should be used with precaution.