Palatal or Middle Ear Myoclonus: This condition is characterized by involuntary muscle contractions in the middle ear, which can cause a pulsating or fluttering sensation. The symptoms described, such as the sensation of a vein pulsing too fast and exacerbation by touching the ear, are consistent with this diagnosis. The alleviation of symptoms by lying flat and neck movement may also suggest a relationship with middle ear or eustachian tube function.

Tinnitus: While tinnitus is typically described as a ringing, buzzing, or hissing sound, some patients may perceive it as a pulsating or fluttering sensation. The triggers for migraines and anxiety, as well as the exacerbation by certain movements, could be related to tinnitus.
Eustachian Tube Dysfunction: This condition can cause a variety of ear symptoms, including a feeling of fullness or pulsation, especially if the tube is not functioning properly. The alleviation of symptoms by lying flat and neck movement may indicate an issue with eustachian tube function.
Benign Paroxysmal Positional Vertigo (BPPV): Although BPPV is primarily associated with vertigo, some patients may experience unusual ear sensations, including fluttering. The symptom alleviation by lying flat could suggest a positional component.

Temporal Arteritis or Giant Cell Arteritis: Although less common, these conditions can cause a variety of head and neck symptoms, including ear pain or unusual sensations. Given the potential for serious complications, including vision loss, it's crucial to consider these diagnoses, especially in older adults.
Acoustic Neuroma or Other Cranial Nerve Tumors: These rare tumors can cause a range of symptoms, including tinnitus, ear fullness, and unusual sensations. Early detection is critical for effective management.
Multiple Sclerosis: This condition can cause a wide array of neurological symptoms, including unusual sensations. While less likely, it's essential to consider multiple sclerosis, especially if other neurological symptoms are present.

Patulous Eustachian Tube: This rare condition involves the abnormal patency of the eustachian tube, leading to a range of ear symptoms, including autophony (hearing internal sounds unusually loudly) and possibly a fluttering sensation.
Superior Semicircular Canal Dehiscence: This rare condition involves an abnormal opening in the bone overlying the superior semicircular canal, leading to a variety of auditory and vestibular symptoms, including sound-induced vertigo and possibly unusual ear sensations.