Yes it wrong to abandon your child(just leaving your child and not taking steps for her safety, well being), but you have options, you always have options. There is something called Safe Haven, and it varies from state to state. Basically if the child is under a certain age, normally 1 year or less. You can go to a fire department, police station, even some hospitals and leave the child with the proper authorities. Some states don't ask for your name but will typically give you a paper to sign for information on the child, like birth date, medical history, etc. You can call there confidential crisis line @ 1.888.510.2229.
We all have to make decisions that are tough in our life. My parents were unfit to raise me(not saying you are not fit just giving an example) and at times I wonder if I would had been better off placed in the system. With every choice there can be regrets, I'm unaware if you change your mind that you will be able to reacquire custody. I'm sure any questions you have the number mentioned above will be able to answer them.
I'm not for or against any choice a person can make, because its impossible to live in someone elses shoes but whatever decision you make try to get two end results. One, your child is safe and taken care of, and Two, you are happy. Life is too short to not be happy.