I'm freaking out because I just don't feel pregnant. Are there any missed miscarriage symptoms? Could I have had a miscarriage and just not know it yet?
Unfortunately, by its very definition a missed miscarriage usually means there are no symptoms before diagnosis. Some women may notice a loss of pregnancy symptoms, but this is a really unreliable sign of miscarriage. (Loss of pregnancy symptoms can occur in normal pregnancies also, especially in the later part of the first trimester.)
What leads to a missed miscarriage being diagnosed is usually when the fetal heartbeat is not detected on an ultrasound or handheld doppler when the pregnancy has definitely reached a point that it should be detected. A followup ultrasound may then reveal that the pregnancy has stopped developing and is no longer viable. A D&C may then be recommended, especially if there is no sign that the miscarriage is about to happen on its own.
It is possible that the term missed miscarriage might also be used if you have developed signs of miscarriage, such as bleeding during pregnancy, and an ultrasound reveals that your baby has stopped growing days or weeks before your miscarriage symptoms started. In this case, the signs of missed miscarriage would be the standard warning signs of miscarriage, ie. bleeding and cramping during pregnancy.
Miscarriage. American Pregnancy Association. Accessed: May 19, 2009. http://www.americanpregnancy.org/pregnancycomplications/miscarriage.html