take time to think about your reasons and choice options
I've had three children and three miscarriages so I understand the loss of a child. I know how overwhelming finding out your pregnant can be, especially if the pregnancy was unexpected. I suggest actually writing out the reasons why you don't want to have a baby then a few days later review the reasons with some close friends/family members you trust and talk about the reasons. Are the reasons fear of the unknown? fear about being able to provide for the child? fear of being an unfit mother? fear about what others will think because you're single/in a rocky relationship/going through divorce?
The choice of what to do is ultimately yours to make. I just urge you to not rush into decision.