First, you need a new endo.
Second, you need to ask that your antibodies be tested--what you've described sounds a lot like Hashimoto's to me, and it's quite common a condition these days.
Third, consider adding 100 micrograms of selenomethionine*to your daily regimen.
I suppressed lifelong thyroid antibodies and a hot nodule using selenium--200 micrograms/day for a year until the antibodies and nodule were gone, followed by a drop to 100 micrograms/day. It's best to get to the lower dose sooner than later, because higher doses increase the risk of type 2 diabetes. (I was unaware of this risk when I was taking 200 micrograms.)
http://www.ncbi.nlm.nih.gov/pubmed/1...?dopt=Abstract
The studies about selenium, nodules and antibodies are equivocal--some have shown excellent results, others not so much, so I'm at a loss about which links to post. Anecdotally, it worked for me, and I know others for whom it also gave good results.
My own endo did nothing but a thyroid ultrasound, and then we kept watch. But I had a known case of Hashimoto's and just one nodule. If it were me, and my labs came back antibody free, I think I'd have the recommended scans.
Be aware that T3 can drive breast cancer. (I tell you this just in case someone suggests natural dessicated thyroid to you as a cure-all.) Also be aware that iodine can exacerbate an existing thyroid problem, so until you know what's going on, it's best not to use it. (I get 100 micrograms of iodine a day from kelp; the rest comes from iodized salt. Although there's a lot of hoopla about high doses of iodine, I'm not convinced it's a good idea, so I keep my intake around 250 micrograms a day.)
(*That's what I used, but I understand that se-methyl l-selenocysteine is also good.)