Sweetie, I'm so sorry you're feeling this way. It IS very common for new moms, but before you reach for a pill, PLEASE consider the following:
1. Having a baby rocks your world in every way. People really underestimate how much and in what ways. Physically, emotionally, spiritually, hormonally...oh, the hormones...they govern your levels of energy, stamina, and mental capacity more that you realize until they go bonkers. This is normal. Crazy, frustrating, and scary - but normal. I have never met a mom who didn't experience similar thoughts and feelings of anxiety and being overwhelmed.
2. Are you getting out? At all? Even a little bit? Getting outside in the fresh air can make a big difference and even moderate exercise is proven to be just as effective in restoring hormone / endorphine balance as mild anti-depressants. I had my son in the fall and it was very difficult to not go stir crazy through the winter months. It definitely affected my coping skills.
3. Is there anyone you can hang out with? Do you have a support system of any kind nearby? I think this is a huge difference between American mothers and those in other countries / traditional communities where everyone is working together, helping and understanding, the normal aftermath of childbirth. Moms aren't as alone. Here, we are really hard on ourselves for feeling like we can't do it all. The simple fact is we can't because we're not meant to. I would suggest starting to network through some local church or moms groups if you have no family nearby.
4. How are you eating? This is HUGE. Yes, baby is depending on you and so you may feel like you don't have time or energy to take care of yourself, but as the saying goes, "you can't draw water from an empty well." You need to take EXTRA good care of yourself by eating regularly and making sure your food choices are rich in the following:
-B vitamins (esp effective in combating depression). Start with some Emergen-C 3/x day w/water. You're hydrating, getting B vitamins which help you feel more energized, and getting electrolytes. This is also great if you're nursing and needing to push fluids.
-iron
-folic acid
-fish oil / omega 3 fatty acids
*People who struggle w/depression typically have low levels of the nutrients above. I would suggest foods rather than supplements for maximum absorption and effectiveness. Please PM me if you need suggestions for foods that will supply them for you.
-calcium/vit D
Try to avoid caffiene, which can increase levels of anxiety and feeling "on the edge".
5. Don't do anything w/the anti-depressant until you find out what the issue is w/your thyroid. Your thyroid gland is your hormonal "command central" - so if things are off, it WILL result in you feeling very off, too. This is very common in my family and the symptoms are what you're describing. Medication will help to restore more normal function.
6. Give yourself permission to take care of you. When I had my son (after a previous stillbirth delivery) I was paralyzed with fear and thoughts that were so alarming I thought I was losing it. I cried everyday, felt scared, and was frustrated thinking I should have been "bouncing back" much sooner / better than I was. I really underestimated the recovery process - I had always thought of delivery as the 'destination' rather than the beginning! Be gentle and patient with yourself.
PLEASE NOTE: I am not a dr or medical professional, only a mom who has vested a great deal of time and effort in learning about our bodies' natural function, needs, and preventive care (namely with regards to diet). I am very wary of AD meds and their side effects, especially for pregnant or nursing moms. I would do everything I could to address dietary/lifestyle issues before taking them. In your thyroid diagnosis (incomplete as it is now) I would take hope. You will have some more answers soon. I would never discourage you from talking to a dr or counselor - even the process of articulating your thoughts and feelings can be healing.
I will be praying for you.
*hugs*