Hi A. :)
I agree with Kym, who suggested it might be postpartum depression. In fact, before I read that, or even got to the part in your msg where you said you are having some trouble with postpartum issues, I thought, "Wow, this sounds exactly like postpartum depression." This is one classic way which ppd can manifest itself.
There are resources out there which can help you. Some try counseling. Others find online support groups (that's what I did - I found a group that talked primarily about my specific issues, and it was a huge help to know I wasn't crazy or alone). There are organizations that can help you find the right kind of help - one that comes to mind is called Depression after Delivery (DAD).
It may be interesting to know that many women who suffer from ppd have been helped tremendously by taking a vitamin B supplement. You might want to check with your doctor or midwife about that. Some others do well on St. John's Wort. These are fairly easy remedies that don't cause a lot of disruption to your delicate and fluctuating body chemistry, and won't hurt your baby if you are breastfeeding. (Breastfeeding also helps ease ppd, as your body releases various hormones that will help you balance out.)
Other things you can do - try "wearing" your baby - get a moby wrap or a maya wrap or a snugli, and keep her with you during the day when she sleeps. You will be able to get a lot done and won't have so much anxiety about how she is doing because she will be right there with you. Some women also co-sleep with their babies - perhaps you can find a side-car sleeper for her, so she is right there with you overnight.
With first-borns, it's very easy to worry a lot, so please don't think you're nuts ;-) But I would definitely encourage you to find some help, so you can be more peaceful and really enjoy motherhood.
-R.