When you stopped the iodine, did you also stop the salt and co-supplements?
Try 1 tsp salt in a glass of water and see if your pulse comes down within about 90 minutes. If it does, you need to supplement salt and water regularly, roughly 1/4 tsp per quart of water, and at least 2 quarts per day.
The co-supplements are also useful for your general health, not just for when you're taking iodine.
It would be helpful if your doctor also tested levels of Free T4, Free T3, and Reverse T3. You can take your own temperature to see if you are in the range of 97.8-98.2 before you get out of bed in the morning.
Please don't get carried away if all you need is salt, 1/2 tsp to 1 tsp each day.