Dizziness is a side effect of the drug Phenteramine but it causes difficulty in sleeping rather than increased sleepiness. For your symptoms, anemia,chronic fatigue syndrome,hypothyroidism, disorders of the hypothalamus,psychiatric disorders like depression and sleep-related breathing disorders should be ruled out.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.