Parenting: 3-Year-Olds Community

Hi, My daughter is 3 1/2 years old. She is in a day care center 2 days a week while I work. The other 3 days, she is home with me. My daughter has been what I would call difficult since she was a baby. Very fussy, screamed a lot, etc. As she has gotten older, she has become a terror. So much so, that I am embarrassed to take her anywhere. I don't know if its just bad behavior or there is something wrong. She throws fits constantly, when she cant have her way, when something goes wrong for her, etc. She is tearing our household apart. Her sister, age 7, told me she cant stand to be around her, because she just bothers her constantly (hitting her, taking her stuff, breaking her things). She is very destructive and rough and seems to get pleasure out of it. She can't sit still, she talks non-stop and it always on the go. As soon as I tell her not to do something, she keeps doing it. I have tried time out, going to her room, spanking, taking away favorite things, making her miss playdates or fun activities. Nothing seems to work. She tells me she doesn't care if I punish her. Its getting to the point where I want to go to work full time so I dont have to deal with this all day. I feel guilty saying that, but its true. I love her dearly and she is a very loving and sweet child, but 90% of the time, she is really naughty. I recently went to the doctor because I have started having anxiety attacks and I know its because of the stress from her. I mentioned her behavior to her peditrician and she said "its just her age, it should get better". Lots of help that was. It's causing problems between my husband and I, both of us are always on edge. She doesn't listen at school and has started to pee in her bed every night, She has been potty trained for a year and the last 6 months now, she just goes in her bed. And if I punish her by putting her in her room, she will pee on the floor on purpose. I feel like she just doesn't care in general. She thinks its funny if she throws her drinks or food on the floor, or throws something at my husband or I or my other daughter. She hit me in the face for no reason the other day with a sippy cup and cut my lip. She laughed. She destorys my things (picture frames, books, etc.), takes markers to walls and furniture. Anyone else have a child who is just out of control? Any advice? I am at my witts end with this child. My first one was so easy and well behaved. Its exhausting!