Hi Michael,
Your baseline should be any recent set of thyroid function tests taken when you've been on a specific dose for several weeks. If you're having symptoms of hypothyroidism, you could always call your endo and ask to have labs then. Or you could ask for a written lab order so you can go in when symptoms occur. If you have an understanding endo and don't have restrictions on the number of times you can have labs, this could work.
If you started out with Graves' disease you could easily have TSH receptor antibodies that are causing your levels to fluctuate. However, if your lipid levels are elevated and you're showing signs of fatty liver disease, your endo might also consider increasing your dose to prevent these transient hypo symptoms.
If your endo isn't helpful, you might also consider having your hypothyroidism treated by a family practice doctor, internist, or osteopath. best, elaine