I am sorry Laura to know about your frustration. The reason your doctor says that the T4 to T3 conversion is not happening in you is because you wanted to know why you are not losing weight. But if you are taking thyroxin for your hypothyrodism and your TSH
has been in normal ranges then you cannot blame your hypothyroidism
for the inability to lose weight or the swelling episodes of your body.
People who experience swelling of body parts are generally having Anti-TPO, ANA positivity and they should opt for healthy lifestyle of weight loss
to avoid more frequency of such episodes.
In short, if thyroid test is normal then there is nothing to worry on thyroid part as a cause of your other symptoms and weight. Take care.