First Trimester and Doctor won't test Thydroid (I have sub clinical hypothyroid)?

Here's the backstory: I've had two unexplained early miscarriages in the past 6 months. The doctor ran all the tests and the only thing that came back abnormal was my thyroid test, so I went to a GP to have them put me on meds. My TSH numbers were 4.81 and 6.41 and she diagnosed me with subclinical hypothyroid and put me on 25mg of Synthroid in late December 2013. She said that the most common reason for early miscarriages were thyroid problems, but she said that I could start trying to get pregnant ASAP and they would test me again in the beginning of February 2014.

My husband and I were very carful NOT to get pregnant because I wanted to wait until they retested my thyroid levels in February, but we (happily!) fell pregnant that same month (conceived around 30th of December and missed my period on January 12th, so I'm just shy of 5 weeks). I saw my doctor yesterday regarding my thyroid dosage and she said they wouldn't up it until the 2nd trimester and that they wouldn't retest me until February as planned.

It seems to me that if I had two miscarriages and the only possible cause (besides just nature) is my slightly underactive thyroid, why wouldn't we check to MAKE SURE the dosage is okay? What if for some reason my TSH rose or just stayed steady at the 3-5 levels?

I KNOW that yahoo answers is not a place for medical advice, but I tried looking online and can't find anything. I thought maybe someone knew the proper protocol based off of their own experience and could maybe help me out. I don't want to go through the process of switching doctors just to find out that this is normal procedure, so I want to be armed with as much information as possible.

Thank you!