@ayesharobaid, so sorry to hear that you are having a hard time. It appears CRA wants proof that your daughter lives with you - what kind of documentation did you provide? Things like the following may help prove she has been with you:
a) record of doctor/dentists visits,
b) daycare/school attendance records(if she is enrolled),
c) do you attend church and can your Pastor give you an affidavit?, etc
d) travel records from CBSA for yourself and daughter(to show when you and the child last entered Canada)
e) photocopies of all pages of yours and the child's passport(s)
f) any other thing you think can prove your daughter lives with you.
CRA is not in the business of cheating taxpayers, neither do they want to be cheated(intentionally or not). They can make mistakes, but the worse thing to do is to ignore them. Call them up, explain your situation and what you are doing to find work, ask for an extension or if you can, make a payment plan for however amount you can afford to start paying back. You don't want them to go into your bank account(which they can do).
You said you were fired for being pregnant - how long ago was that? Did you apply for EI? If not, you should apply immediately and explain what happened. Service Canada will get in touch with your employer, etc and go from there. You may still be eligible for EI benefits even if you were fired. This way you will be able to support yourself and your daughter without much hardship.
Next, visit your local legal aid office. If you were indeed fired for being pregnant, you may have a good case against your employer. Some lawyers will take a case and charge the client after they have won their case(settlement). If you agree to such a deal, make sure you get the agreement and the fees you will have to pay in writing. Please don't just sit back and feel sorry for yourself, fight for you, your daughter and unborn child. Congrats on the impending addition to your family and hope it all works out well.