Thanks for posting and I am sorry you've had such dreadful symptoms and despite your long thyroid journey can still encourage others who are starting out on theirs.
Have you had a recent blood test because your dosing doesn't seem right, i.e 125mcg one day and 15mcg the next (I am assuming it is mcg as you have stated mg).
I am also sorry you are on levothyroxine alone (and I'm not medically qualified) that you are not on a combination of T4/T3 as you have no gland whatsoever.
Blood tests should always be at the very earliest, fasting (you can drink water) and allow a gap of 24hours between last dose and test. I think the doctor should also test your Free T4 and Free T3 to accurately assess how much T3 is circulating.
In fact I think you should ask for a Full Thyroid blood test, i.e. TSH, T4, T3, Free T4, Free T3 and B12, Vit D, iron, ferritin and folate. All have to be optimum levels, not 'somewhere' in range.
Levothyroxine, as you know, is T4 alone. It is inactive and has to convert to T3. T3 is the only active thyroid hormone required in our T3 receptor cells and without sufficient our whole body suffers.
I am glad you were also able to bring up your children despite your health problems and at times it will have been well beyond what most of us experience.
Post your results with the ranges for comments after your next test.