Forshelby, show me a mother who has never felt that way and I will show you a liar. Some babies do challenge us more than others, but having to do it all on your own is always giong to make it hard to cope. We are not designed to parent alone, but sadly that's the way it works out in our society more often than not.
You don't need to apologise. And feeling you can't cope does not make you a failure as a mother, it just shows that you need help (and we all need help)