please tell me I am not a monster

My junior year of high school I moved two states away. Needless to say it was a very long and lonely school year with no friends. I met my husband during the first couple of months after I moved, when we turned 18 we got married and became pregnant with our first daughter Emily(3 1/2 now). I have been a stay at home mother since I became pregnant with our first daughter. Our marriage is amazing, our first child was such a blessing and made everything feel like it was fitting together perfectly. Emily is such a beautiful social butterfly, so intelligent, and raising her had been an absolute breeze. She listens to everything we tell her, she just doesn't do anything she isn't supposed too. She was the happiest and brightest baby, even during teething time she hardly fussed at all. Then we had our second daughter Abigail(7 months now) we were also very excited during the pregnancy and we were so excited to see our family grow. She has been just a delightful as Emily and watching her grow has been great. A couple weeks ago my husband and I found out that we will be having a THIRD child(I am currently 11 weeks along). We are still super excited to add yet another addition to our family, however, I am not sure if it is hormones or what. I have been extremely depressed the past month. Abigail has been teething and it seems like she is so unhappy. It seems like all she does is cry all day, every day.. No matter what I do she isn't happy. My daughter Emily seems like she has been acting out all of a sudden - and I am sure that it probably all the changes of having siblings, so this I can understand. I feel terrible, I feel like in my frustration of Abigail being so unhappy that I don't want to be around her, or interact with her. I push her off onto my husband because I just CAN'T listen to the crying anymore. Then I am frustrated that I am frustrated with my baby girl. To top it off I also feel horrible because right now finances are extremely difficult and we have had to ask for a lot of help from family. I am constantly asking myself - "Why are we having another child if we can't even afford to take care of the first two??" and then finally I am asking myself "why am I even a mother if I cant deal with the crying of my children?" I feel like a terrible, neglectful mother.

I don't know if this is hormones, or the excited burning out child after child. I don't know if it is because I stay at home day after day, I don't know what questioning all this means.. I have no friends and the only family I know in this state are my parents. I don't ask or have anyone babysit. Since my children have been born there have been 4 times that someone has babysat my children for a few hours. Right now I am just so unhappy about the way my life is, I feel stressed and depressed by everything going on. I love my children so deeply, I really do. I am just wondering if anyone can relate to these frustrations??