Fluctuating levels of thyroid antibodies can cause your TSH, T3 and T4 to all fluctuate.
Right now, I would watch your levels closely and see what happens over the next few months. It would warrant having TPO and Thyroglobulin antibodies checked.
TPO antibodies attack the process that makes thyroid hormones in your thyroid gland and can cause levels to drop.
Thyroglobulin antibodies attack the protein that binds thyroid hormones in your blood and within the thyroid gland, causing T4 to be released and in so doing, can cause a rise in Free T4, sometimes very quickly.
I am not a doctor, nor have I ever played one on TV...