Someone tell me what to do

I have a goiter, um it's like my thyroid is enlarged - other than that I'm no help in defining goiter, ok? So I have a goiter and this was found via cat scan in August. Then an ultrasound, which recommended that I should have the Thyroid swallow test thingy done (You swallow a radioactive pill and they take pics of your thyroid to determine it's function, etc.) BUT, you can't have this test done until 90 days after a test like a CT scan where you have the iodine or whatever it is they use in CT scans injected into your blood stream.

Ok so now it's approx 90 days later right? My family dr was not going to medicate my thyroid but did not really explain why, just that after this test he would. My OB/GYN's opinion was "why the heck not? I'll write the rx myself, you need to have your hormones under control." So I chose to go with my ob/gyn's answer. So I changed family dr's cause I don't really care for the one I was seeing and he says "I agree with your OB/GYN - let him treat it, but I'll go ahead and order that swallow test for you." Never mentions, maybe he didn't realize, although he knew I am taking Synthyroid, that I would have to go off Synthyroid for 1 month before the test.

Now this is not a test you can do while pregnant, so when I got pg I just took it as a sign this would be a test we'd just have to do another time. Now I'm not pregnant. Due to the holidays and my having to get off the Synthyroid for 30 days, I can't have the test done until Jan 3rd. I could TTC (not actively, we're just not going to use birth control this month, of course) and if I got pg just cancel this test....but there is NO WAY I will even ovulate without the synthyroid, not to mention how HORRIBLE I'm going to feel. My hair falls out, I'm tired, I gain weight, my skin is dry, I'm really cold, it's NOT fun. And now that I feel so much better I don't want to go back to feeling like crud!

So now what do I do? I have to stop the Synthyroid on Dec 5th if I'm going to have the test done. I have a dr's appt that day so I might just go ahead and bring it up with him. But I lean towards, why are we doing this? We know my thyroid doesn't work because I'm on thyroid meds. Your thyroid doesn't just start producing TSH, you can have a thyroid that produces too much get better and start producing the right amount, but I simply DO NOT MAKE the hormones, hence the synthetic hormones I am on. Can't we just monitor this thing with u/s? (the goiter) I just don't want to feel that awful ever again.

So what would you do?