You need further investigation. Please meet an Endocrinologist as soon as possible to get an accurate diagnosis for the hypothyroidism. Only then can you know about diet and other precautions. Some
thyroid diseases go on to become cancers. Don't you want to be forewarned about it?
Nobody like to take medicines but if you need to, you have no choice about it!
However, start the hormone replacement as prescribed by your existing doctor immediately.