You are not taking too much iodine. However, my experience was that even with Iodine and selenium, my thyroid was not up to responding to them. It struggled to perform, and I ended up with a goiter. I had to use thyroid hormone -- first NDT (natural desiccated thyroid which combines T4 with T3) and then T3 only -- before my goiter would subside. I continue to need thyroid hormone and now can make full use of Iodine and the co-supplements.
Whether this is happening to you, I can't say. But it bears looking in to.