Dought and Clear, - Rulings on Tawbah, - Permissibility of a fornicator Marrying a Believing Woman.

Please tell me, can I marry a beliver if I`ve had sex with a
non-Muslim? Please answer.
Praise be to Allah.
If a fornicator repents sincerely, Allah accepts his repentance. Allah
says (interpretation of the meaning):
"And those who invoke not any other ilaah (god) along with Allah, nor
kill such person as Allah has forbidden, except for just cause,
norcommit illegal sexual intercourse and whoever does this shall
receive the punishment. The torment will be doubled to him on the Day
of Resurrection, and he will abide therein in disgrace; Except those
who repent and believe (in Islamic Monotheism), and do righteous
deeds; for those, Allah will change their sins into good deeds, and
Allah is Oft-Forgiving, Most Merciful. And whosoeverrepents and does
righteous good deeds; then verily, he repents towards Allah with true
repentance" [25:68-71]
See also question no. 728.
If he repents, then he may marry a believing woman. If a fornicator
repents, he should conceal his past and not spread word of it.
And Allah knows best.