Your symptoms sound highly suggestive of hyperthyroidism, with perhaps a bit of postpartum depression thrown in there. In short, you sound miserable. I think the sooner you can see an endo the better, because if you are hypothyroid it isn't likely to get better without treatment - in fact it can get much worse. And yes, it can definitely be life threatening.
Hyperthyroidism speeds up everything in your body - including your heart. My normal resting heart rate is in the 60's; when I was diagnosed it was 120. This means my heart was working twice as hard and aging twice as fast. Also, your mood swings could potentially present a danger to your children.
You said your child was born in June, but from your comments it sounds like it maybe was January? If your six-month check is in June, I wouldn't wait that long. One possibility would be to see if you can get into your primary care physician and if he or she will order a thyroid panel for you. This should include TSH, T3, free T4 and thyroid antibodies. If you can get this done and post the results here (including the lab's reference ranges), both we and your doctor can probably help you more. This would also give an idea of how quickly you need to see an endo.
Good luck, and keep us posted.
Added: for your reading pleasure, since I know you have so much free time with an infant and a toddler, here's a link to a Mayo site that talks about
possible consequences of continued hyperthyroidism:www.mayoclinic.org/diseases-conditions/hyperthyroidism/basics/complications/con-20020986