All Praises are Due to Allah
Islam erases whatever took place before it and after Allah guides you there is no sin on you, regarding something which took place in the past. The rule according to the Shariah (Islamic Laws) is that the child is to the bed and follows the husband, unless he washes his hands of the matter.
The child in not considered to be your son, nor do you have any responsibility for him. So start a married life according to Islam.
May Allah forgive you and increase you in protection.