Aww, sorry to hear youre feeling sad today. Sounds like it could be a slight case of hormones there? You have been blessed with so mych goodness, embrace it and give thanks. Hope you feel better soon, not long to go!!!
It sounds more like antepartum depression. Don't be hard on yourself - you can't control your chemistry. Talk to your doctor. I'm sure he\she can help.
Dont worry. .. its just one f d symptoms of pregnancy.... especially during third trimester. Everything will b okay later.
Hormones and emotions. Like someone else said mention it to your dr. It is helpful for them to know, that way they can be mindful especially for after baby comes. PPD affects a lot of women and you may be prone to that after baby is born. They see it all of the time so don't be ashamed or anything, you may need help with it at some point and no one will know unless you tell them. :)