If I added a small amout of T3 to my Thyroid dosis (and took away a bit of Thyroid) would I then be able to see a difference. I am sorry my head is filled with cotton today! I mean: could I take a kind of test with a very small amount of T3 togeether with my Thyroid. Would I then be able to see if the T3 only maybe was a solution?

You wrote another place
If someone has spent several years trying to use natural thyroid and their iron is Ok and everything else is OK and they are still unwell then T3 should be tried. Doctors try to tell people that there is 'some other problem' but it is rarely true - it is usually because the thyroid hormone treatment is not working.
I feel I could be one of those people! I have been using NDT/Thyroid for 3 years now. The latest months I have a feeling of moving backward into worse conditions.

I have tried to take Thyroid in the night (CT3 Metod) some nights now. I wake up with a heatbeat in the night, like 3-4-5 o'clock. But I still have that heartbeat after taking my Thyroid. And cannot sleep the rest of the night. You said earlier
You need to be using the Circadian T3 Method to raise cortisol. If cortisol is higher then cellular glucose and ATP will be higher and you'll get more FT3 and less reverse T3 - this is a big area.
So my question is: is my reaction to take Thyroid in the late night a kind of proof that I should start on T3 only?

Tonight I will start on my first dose of LDN, 1.5 mg.