God forgives sins. The sins we committed before we were believers don't count against us but we will live with the consequences. The sins we commit as believers will affect our eternal reward in heaven.

David and his family suffered for his sin with Bathsheba and against Uriah the HIttite. His newborn son was struck dead. His son Amnon raped his daughter Tamar. His son Absalom had Amnon killed then he rebelled against his father. Most likely, hundreds of people died because of David's sin.