Medical issues that can prevent weight loss despite exercise and diet?

Medications??? Certain medications such as steroids, antidepressants, antipsychotics, antiseizure medications, diabetes medications, high blood pressure medications, heartburn medications can interfere with weight loss or cause weight gain. I note you are on metformin and Phentermine which can both contribute and your Cytomel (liothyronine) indicates you have hypothyrodism, which may be under-treated.