Dizziness seems a very common ME / CFS symptom. According to this study the single most common cause of general dizziness, is spinal canal narrowing (spinal stenosis). As already mentioned in other threads, spinal stenosis is strongly implicated as a causative factor in both fibromyalgia and CFS. If dizziness is one of your main symptoms, it is quite possible that a structural problem might be the root cause.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5981019/
A 15-month retrospective study of 1,000 outpatients was conducted to determine the exact cause of general dizziness. The most common diagnosis in all analyzed cases was cervicogenic general dizziness (89%). The majority of the patients who underwent magnetic resonance imaging of the cervical spine had narrow spinal canals. Measuring the anteroposterior diameter of the spinal canal in each case was critical to obtain an accurate diagnosis in line with the diagnostic criteria used.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5981019/