From what you've written, I think it sounds more like anxiety than depression. It doesn't seem like you have a chemical imbalance problem but rather a difficult time coping with your family life circumstances. My advice- speak with a psychologist, not a psychiatrist. A psychologist can help you work on your anxiety issues. If the psychologist feels that you are in need of medication, then he or she can refer you to a psychiatrist. In addition, I think it'll be beneficial for you to join a support group for parents of children with exceptionalities.
It sounds like you are experiencing some depression. You have some classic symptoms. Many of us suffering with depression function normally and hold full time jobs. If I were you, I'd see a psychiatrist for an evaluation and go from there. It may be that therapy is all you need, and if medication is needed a psychiatrist is most knowledgable with these types of medications. You're not alone, in this faced paced world and all that goes with it, there are many sufferers. It is no different than any other medical condition that we would need help with. We have the specialist to help us, and we owe it to ourselves to get the help needed. You may just get over-whelmed at times with dealing with your daughter, and you may have some anger issues as well. This is where therapy is a big help in teaching us how to cope better and think in a more positive manner. There is nothing to be afraid of, if you were told you had diabetes, you wouldn't think twice about seeking medical help...this is no different. I wish you all the best and take care.