Test if both sides of your nose block equally or only one (put a knuckle
against one side and brethe in and out to see which is open).  Try at different
times to look for a pattern.

But daily body hormonal and other cycles are normal.....

Do you remember when your sinus problems first started, and can you relate
the start of your misery to some event?

You say, that from 9 or 10am, to about 3pm, your sinuses are "tolerable".
What does that mean? How are your sinuses during that time period.

Have you ever had a full day where your sinuses have been OK?

Have  your doctors ever discussed food allergies with your? Have they ever
discussed a possible infection?

Have your doctors ever discussed not charging you for the visit, since they
either don't want to take the time to solve  your problems, don't care, or
don't know how?

I don't know much about the body's circadian rhythm, in influencing gland
activity throughout the entire day. But, I have done some research because,
some of my problems start getting  worse from about 8pm and start improving
after 2am.

I have read, for instance, that the Pineal Gland, among others, becomes more
active at night and then peaks in activity about 2am. The Pineal Gland
produces Melatonin, which is supposed to induce sleep. Melatonin can also
have some other effects, which are more related to my problems.

I haven't done a lot of research on this, but I do know that it happens. You
might want to find out if your circadian rhythm might be part of your sinus
"cycle". I don't pay too much attention to my circadian rhythm, since I
can't do anything about it. I just want my sinus problems fixed!

If my sinuses start to ache, I irrigate and flood my sinuses "upside down"
immediately to flush any "crud buildup" out of them. When my sinuses start
to plug up, and they stay plugged for three days or more, and seem to be
getting worse, I also irrigate my sinuses, because I assume I have gotten a
sinus infection. For me, flooding my sinuses, "upside down", with a
"diluted" mixture of 3% hydrogen peroxide, baking soda and salt treats any
sinus infection that I have, or helps to remove junk that has accumulated in
my sinuses and needs to be flushed out.

Best of luck in finding out how to solve your sinus problems, and in getting
relief.