I was with my 2nd, but I attribute it to gaining too much weight. I gained almost 100 lbs and was feeling really bad about myself. Luckily I had to hold it together for my baby that I had already, they are 17mo apart.
I'm 27 weeks pregnant with my first and I am very very emotional and on edge all the time. Every little thing makes me cry or want to pull my hair out. I just gained my first couple pounds last month and that made me feel like a failure because I felt that I wasn't gaining enough. I've been told that it's normal to be moody and emotional but if its to an extreme you might want to mention it to your Dr. so that you can get the proper care because depressions during pregnany could lead to serious post partum (or so i've heard). Hope I Helped Good Luck.