Artmouse - you say you have an underactive thyroid and are finding it difficult to lose weight - could it be that your medication needs increasing a little? Do you have return of other hypothyroid symptoms eg fatigue, feeling cold etc?
re weight loss diet and exercise. The right type of exercise ( toning, strengthening, body conditioning workouts etc) build muscle which weighs more for a given mass (volume really) than fat does so you may weigh more but replace fat with muscle. The more muscle you have the greater your resting metabolism so the more food you can eat without gaining weight and the more calories you burn at rest.
So - that's the first thing - even with back issues try to find a regime that involves working and strengthening all your muscle groups. Pilates is good but you need to do something perhaps more intense or have a regular daily workout maybe?
Secondly what is your diet like? You do not need to count calories in order to lose weight. I never do. You just need to know what sort of foods to eat, and when to eat.
Can you talk us through a typical day (honestly) including snacks and drinks?
I have lost and gained weight for much of my life especially since finishing having children - irrespective of HRT. In fact I put on most weight during peri-mnenopauase when I didn't realise my metabolism had slowed. Remember as we age we need to exercise more and eat less just to stay the same.
I also have a rule never to buy bigger clothes - that is the best weight-loss strategy and my tip of the day

. When my waistbands/trousers start getting difficult to do up - I know it's time to ease off. Now is that time! I need to lose about 4-5 pounds. My weight only varies by about half a stone but I can never keep it at the lowest amount that I reach!! Also keep a note of weight and measurements every so often just to keep myself in check!
Main thing is to cut almost all added sugar and pure carb foods especially refined ones and eat less fat, more lean protein and tons of fruit and veg. Also to stop eating when you're full. Eat a good breakfast. Don't eat after 6 pm or try the 8 hours window eating diet (eat everything - well most - within an 8 hour time slot - there are lots of different things to do....
Can you tell I've thought about this a lot?! I am one who has to keep her eyes on the ball always in order not to get fat!!!
Hurdity x