Headaches caused by my sleeping position?

[nmarman]

There are two headaches that fit your distribution:
Cervicogenic coming from the trigeminalcervico nucleus referral pattern.
And occipital musical referral (trigger point head ache)

From the sounds of it It maybe cervicogenic because it should feel better at rest if it was sub occipital muscle referral. However it is common to have elements of both.

NOTE: people go use very high pillows can create sub-occuptal m. referral from sleeping/lying when on back and reading book in lap.

Easzierly solved (if you have only had symptoms for a short period) with education about aggravation factors, manipulation (cervico genie h\a), massage for sub occipital area.

Given there are possibilities of structural instability ie kyphosis of cervical region and other issues it is best to have this looked at first (x-ray).

Fasiculation??? You mentioned can be a sign of neurological impedance - especially if it happens on tongue? Does this happen?