Re: Help I know nothing about this!!
Sounds like you're doing everything right. BEFORE you go on Prozac (or any other antidepressant), definitely seek the advice of an Endo and request the Thyroid tests Treefrog suggested (Free T3, Free T4, TSH, and maybe Thyroid Antibodies if you can convince them do so). You may have been borderline hypo before your pregnancy, but often pregnancy can tip the scales a bit. Antidepressants can mask the symptoms that you need to use as your guide, and some antidepressants don't work well with thyroid supplements.
If your doctor won't test for these things, find one who will. Or do a websearch for labs that will allow you to have these tests (by blood or by saliva) without a doctor's referral and then bring your results to your Endo to discuss. Thyroid.About.com has the (commercial) reference for a blood lab, but there are several that do saliva tests. Just query on "thyroid saliva panel." It's a good idea to get these tests as a baseline of your condition (to match up with your symptoms). You may not be hypothyroid, but it's one more thing to rule out.
If you've not looked recently, the Information Archive has those great hypo (and hyper) symptoms lists. Plus, there's a recent post of questions (and hoped-for answers) to use when seeking a new Endocrinologist.
There are also supplements that may be able to help you if your blood/saliva tests show that you are in the normal ranges. Selenium helps the body properly metabolize thyroid hormone, and an herb called Maca helps with general hormone imbalances. Calcium, magnesium, zinc, and copper are also important to keep us balanced.
Good luck, and keep us informed.