Next time, ask your doctor if you can go on Cytomel until two weeks before. It's a different type of thyroid hormone that clears out of your system quicker, so you only have to be off of it for two weeks.
You may be able to have the RI quicker. Call your doctor and ask about it. He may want to do a TSH test to make sure your thyroid hormones are low enough for the test to work properly. Tell him about your symptoms, that you are having trouble functioning, and that you are worried about it getting worse over the next two weeks. Different people process thyroid hormones differently, so you may not need a full six weeks. There is no harm in checking your TSH.
Does your doctor want you to go on a low-iodine diet? If so, have you started that or when are you supposed to?
Again, next time, you can probably have the TSH-Stimulated (Thyrogen) shots instead of going through withdrawal--although the shots are expensive. If your insurance won't cover it and you can't afford it, ask about Cytomel next time.
If you have any other questions or just need supportive words, please feel free to write back. A lot of people on here, including myself, have been through what you are going through. It's not easy, but it will be over soon.
Do you have people around you to support and take care of you? Are you ready to take all the precautions for the RI?