If you are asking if you will be granted rights to live in the UK simply b/c you have fathered a child by a UK citizen, the answer is no.
As the others have said, you will need to marry the mother of the child and prove the two of you can support your family without access to any additional public funds for YOU in order to be able to live and work in the UK. (unless you qualify for a work based visa or plan on going back to school)