I'm taking amitryptiline now for almost 5 weeks. My sleep was very good in the first 2 weeks, but since then I only sleep about 7 hours a night.

What happened is that I am still very tired during the day, without beeing able to sleep. The tiredness is somehow sublinimal, meaning that I do not yawn all the time or my eyes keep shutting down, however I feel like a zombie.

Overall my mental condition is better than a few weeks before(less thinking fatiguing) but physically it started to develop into the opposie direction.
And what worries me the most is that, in some situations my speech becomes even slurred,because of the tiredness.

The point is I didn't have these feeling when I slept well in the first 2 weeks. Is it maybe the cumulative deprivation of sleep or a sudden intolerance of amitryptiline? My doctors couldn't tell excactly where it comes from.

Did anyone experience something similar?

Didn't do a thing for me except gave me hangover feeling in the morning, but I was only on 10mg. Anyway, I thought 7 hours sleep is a decent average for most folk?

Well I saw more people sleeping 12 hours a night than 7 hours on amitryptiline. I did that too, but only in the first 2 weeks.

And yes, I had also that feeling to be a bit drunk(when I had to get up without sleeping late).

You may be over-thinking this. Anxiety will cause fatigue. The amitrptyline is to help with head aches and getting to sleep. It is not to help you continue to sleep. As said, 7 hours is not bad. Many would love to get 7 hours sleep.

Taking a short nap during the day would be good.

Drugs like amytritaline are not meant to be taken for extended/regular lengths of time. I had similar to what you have described, and noticed that it made my mood more negative too. So I stopped taking it and felt better. My understanding is that this is a common reaction. Hopefully you are ready to forge your own sleeping/energy pattern, but if not your Dr will be able to discuss/prescribe an alternative.

(Those symptoms/advice should be printed on the inner label thingy)

Amitriptyline CAN be taken every day for extended lengths of time. It is an older tricyclic antidepressant that also works for nerve pain. I've been on 50 mg. at night for almost 5 yrs. I have had good results helping me fall asleep, and it helps my headaches and facial numbness feeling. That dopey daytime feeling went away with time.