All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Zina is a major sin and Allah warned us against it. Allah Says (what means): {And come not near to the unlawful sexual intercourse. Verily, it is a Fahishah [i.e. anything that transgresses its limits (a great sin)], and an evil way (that leads one to Hell unless Allah forgives him).} [Quran 17:32].
If you have committed this sin, repent to Allah, feel very sorry for what you have committed and promise to Allah never to commit this sin again. If you do this, know that Allah accepts the repentance of those who repent to Him. Allah Says (what means): {Say: "O ‘Ibaadi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allah, verily Allah forgives all sins. Truly, He is Oft-Forgiving, Most Merciful.} [Quran 39:53].
You should not tell what you have done to anyone. Since Allah has concealed your sin so do not reveal it to anyone. The Prophet, sallallaahu ‘alayhi wa sallam, said: “Whoever commits any of these bad acts, he should screen himself with the cover of Allah and never reveal it as whoever discloses to us what he has committed we will apply retributive measures on him”.
So, if anybody wants to marry you do not mention to him what you have committed.
Malik reported in his Book of Hadith that a man offered to marry the sister of another. The latter told the former that his sister committed Zina before. When Caliph Omar Ibn Al Khattab, may Allah be pleased with him, heard the news he called the brother of the girl and said to him angrily: “Who told you to disclose this information?”
If someone wants to marry you do not tell him anything about your past sins unless he makes it a condition from the very beginning that he wants to marry you only if you are virgin. In this case, you could tell him that you are not accepting his offer without disclosing to him the reason. You should also pray to Allah as much as you can. Ask Him for forgiveness.
In addition, the Sharia does not require you to ask for the "lashes penalty" even if you live in a country where the Sharee’ah is applied.
Allah knows best.