Having Symptoms Of Hypothyroidism. Need To Take Medication On Confirmation Or Corrected By Diet Control?

I believe I have symptoms of an underactive thyroid = cold hands + feet, brittle finger nails , dry skin , hair loss , poor muscle tone , occasional light-headedness, poor memory,occasional fatigue, occasional constipation, occasional depression, occasional mental fog, occasional mood irritability , prediabetes sugar level (100-110 up to average of 145 aprx 2hrs after eating, occasionally 165 after a big carbo meal). I am 62yrs + 20yrs menapausal but otherwise appear to have a good immune system as I rarely get sick. I have had these symptoms most of my life but had not figured these symptoms to all be related under one problem till recently. Lately I seem to be worsening especially hair loss, mental clarity, + light-headedness. My job is pretty stressfull working 60-70hrs wk as a truckdriver + gives me very little exercise. I grew up in a household that did not add salt to foods as my mother had high blood pressure. I am currently slightly overweight (5 4 140lbs). My question is: if I have tests done to confirm hypothyroidism will I have to take the hormone medication for the rest of my life? Or by adding selenium & iodized salt to my diet can this now be corrected? (how much?)Or can you reccomend other natural herbs/Ayurvedic supplements/diets/precedures? How long does it usually take to correct with treatment or is it too late for me to bother?