AW,
Repentance is the keyword, because repentance wipes away all former sins. If you repent sincerely and follow the conditions for it i.e. stopping the sin, feeling sorry about the sin, and vowing to never return to it. Then you are granted the title of non-fornicator, a former sinner can then marry a chaste spouse & enjoy the fruits of a blessed marriage that is legal.
However, if a fornicator does not pray, his repentance will never be accepted. First thing is to establish salaah, then repent, then sever contact with former girlfriends/booty calls and then you can marry. There's always a 2nd chance. Also, if someone who was married once ever has illegal sex, he will be considered an adulterer. Once nikaax takes place even if widowed or divorced, you'll always wear the title. You will be stoned rather than whipped.