You are right in that not all people have antibodies but they can have a failing thyroid gland which is hypothyroidism. If you have antibodies it means you would have an Autoimmune Thyroid Disease (hashimotos) and the antibodies are attacking the thyroid gland and you would eventually be hypothyroid but in the meantime you could swing between hyper (too much) and hypo (too little) thyroid hormones. A thyroid gland which is not providing sufficient thyroid hormones it is called Hypothyroidism and they go only, usually, by the result of the TSH.
You say you are 100mcg of levo since you were diagnosed which is a bit unusual as 50mcg is usually a starting dose with a 25mcg increment wiith a blood test about every 6 weeks till you feel well.
You don't say whether you are having clinicial symptoms at present on 100mcg levo.
If you've been on 100mcg of levo since first diagnosed I would ask for a new blood test. Ask for a full thyroid function test if you're still not feeling well, which is TSH, T4, T3, Free T4 and Free T3. The labs may not do them if your TSH is in range.
You should also ask for a Vitamin B12, Vit D, iron, ferritin and folate if you've not had them recently.
When your next blood test is due leave about 24 hours between last dose of levo and the blood test which should be as early as possible, fasting, and take levo afterwards. Get a print-out of your blood test results and post with their ranges for responses from members.