My partner gets migraines which impair him, and effect his life has had scans, tablets nothing has worked has also changed diet/sleep/activities ?

Migraines : Another possibility to look into is medication overuse headaches. Sometimes, medications intended to help may end up causing a headache if used frequently. Headaches worsen before improving after stopping the medication. Chemical meningitis or increased intracranial hypertension (pseudotumor) may be other considerations. However, these may require invasive procedures to investigate further.

Neurologist. : Sounds like it's time to seek a headache specialist. They are usually neurologists. Good luck.