Wow,
@alanmia, it has been a while! I skimmed your posts from 2015 and 2019, and it's clear that you understand what's up, and that you did the work in 2015 and experienced significant success, with a relapse in 2019, and here you are again. Not at all unusual especially in these tough times.
I always want to remind people that we are not medical professionals and we are not actually able to diagnosis TMS with zero knowledge or examination, and that new symptoms should be medically checked out, even in experienced TMSers if applying TMS techniques does not bring relief or changes.
With that caveat out of the way, I know that you know the answer, and you're just seeking some reassurance. If Dr Google doesn't have anything to say about hypnic headaches except to describe them, then it's pretty obvious that hypnic headaches are TMS.
And if your extensive knowledge about TMS eliminated your first headaches quickly, only to be replaced with a new and more sophisticated headache shortly thereafter that is defying your skills - well you know how the Symptom Imperative works as well as I do, right? Your brain is apparently not going to let you off that easily this time around.
Which means it's time to revisit the emotional work to figure out why your brain is trying to distract you with these symptoms. People report that re-reading Dr Sarno or Steve O is very helpful. Others that they simply pick up pen and paper and start writing. I go for breathing and mindfulness, plus writing.
Go back to the SEP and the writing exercises (since you mentioned that journaling worked for you in 2015). Or you could check out Alan Gordon's Pain Recovery program which he generously donated to us in I forget what year, perhaps later than 2015.
A few weeks ago Nicole Sachs repeated an excellent podcast episode on the Symptom Imperative, because so many people are struggling and relapsing recently - it's referred to here:
https://www.tmswiki.org/forum/threads/nicole-sachs-on-long-covid.26924/ (Nicole Sachs on Long COVID)
Also these two recent ones:
https://www.tmswiki.org/forum/threads/nicole-sachs-podcast-s3-episodes-29-and-30.26965/ (Nicole Sachs podcast S3 Episodes 29 and 30)
Sorry you're back, but it's undoubtedly the right place for you to be so welcome again.
~Jan