You have Hashimoto's thyroiditis which is the most common cause of hypothyroidism in developed countries.
Excerpt from Hypothyroid Mom - Top 5 Reasons Doctors Fail To Diagnose Hypothyroidism...
"Thyroid Tests "Normal" But You Don't Feel Well?
If you're undiagnosed, or a thyroid patient taking thyroid hormone replacement medications, being in the "normal" range does not mean you feel well, or that your treatment is optimized. What levels are considered "optimal*" by many integrative physicians?
~ TSH - Typically less than 2.0
~ Free T4 - Top half of the reference range
~ Free T3 - Top half - top 25th percentile of reference range
~ Reverse T3 - Lower end of normal range
~ Thyroid Peroxidase Antibodies (TPO) - Within reference range
~ Vitamin D - Above 50
~ Ferritin - Above 60 (Above 80 if experiencing hair loss)
* we are all different, one size doesn't fit all, so these are guidelines. Your optimal levels may vary."
Just to add, for those who don't live in the US, Vitamin D - above 125 nmol/L.