Childcare is the expense that could blow you out of the water. Do you have any relatives that can help out? If not, begin tomorrow your search for affordable options.
With a child, you should qualify for the Earned Income Credit which could give you back several thousand in your tax return.
As others have said, apply for WIC and be sure to get good prenatal care.
Your low rent is a big help. How stable is that situation? If your rent tripled, you would be forced to make some very tough financial decisions.
You don't show a car payment? Is your nearly new car paid in full? Even without a car payment, your car expenses are very large as a % of your income.
How close