Praise be to Allah.
Firstly, whoever repents, Allaah accepts his or her repentance.
Secondly, if the pregnancy and birth happened before the marriage contract took place according to sharee’ah, the child takes the adulterous mother’s name, not the adulterous father’s. The child still has rights according to sharee’ah and he should be given a good upbringing and cared for properly.
Thirdly, you should not despair of the mercy of Allaah or say “Allaah will not forgive me.” “No one despairs of Allaah’s soothing mercy except those who have no faith” [Yoosuf 12:87 – interpretation of the meaning]; “And who despairs of the mercy of his Lord, but such as go astray?” [al-Hijr 15:56 – interpretation of the meaning]. So long as you have repented, you should have the hope of mercy from Allaah.
Fourthly, you will find a detailed answer about repentance from zinaa and a lot of information to make you feel better, in the book “"I Want to Repent, But...", which is published in the “Books” section of this website.
Fifthly, what is in the past can be dealt with by repenting. From now on you have to try to do a lot of good deeds, because good deeds wipe out bad deeds and raise a person’s status. We ask Allaah to forgive your sins and help you adhere firmly to His religion. We wish you a future filled with good deeds and acts of worship. May Allaah bless our Prophet Muhammad,