Thank you everyone for your responses. We got a new look into our situation. She a has a cold most of the time, which the Dr. said can be normal since her older sister is bringing home germs, and then her and her twin pass it back and forth which definetley makes her fussy. The Dr. also told me that they are teething from about 6 months to 2 years and right now she is getting in 4 teeth at once. He also said that some children have really bad pain when they are teething and others have minimal pain... I am guessing she is one that is a little more sensitive to pain. He said that seperation anxiety peaks at 18 months, and it sounds like she is going through that too. He suspects that she has asthma, b/c every time she gets a cold she has some pretty bad respiratory issues. She has inhalers, which help. I am sure too that it is hard to be a twin and have to share everything with her sister. I guess everything combined is making her one grumpy child.
We do have some good days, but they are few and far between. It must pass soon since the weather is getting nicer (maybe she will get fewer colds?), her teeth should be all in soon, and the seperation issue can only get better. Until then we just have to keep doing what we are doing, Love her and cuddle her and let her know that we are here for her.
Thanks again everyone.