Hi Jan,
Do you have Hashimoto's thyroiditis? For HT, the recommended dose is only 1.5 mg and some people take it every other day. You might try taking your dose every other day. Some people also take it once or twice a week since you're not working with therapeutic blood levels of the drug. Rather, you're looking for the increased production of endorphins that results around 5 hours after your dose. For now, I'd use LDN either every other day or every 3rd day so your body can adjust to it.
LDN, especially at that dose, shouldn't cause your thyroid hormone levels to fall. The fibro like symptoms are usually caused by a move into hypothyroidism.
LDN doesn't cause physiological weight loss (like due to increased metabolism). What it does is usually cause people to have a greater sense of well-being. Some people report that this keeps them from binge eating and chocolate cravings. I wasn't lucky enough to have this happen.
Because the fibro symptoms and achiness are more characteristic of hypot and weight loss is more likely to be seen in hyperthyroidism, it's not likely that LDN is affecting your thyroid status. It typically works by reducing thyroid antibody production so effects on thyroid status take several months although improvement in thyroid eye disease occurs sooner. Best, Elaine