In the name of Allah the most Gracious and Merciful. As a human and being a Muslim if you had committed sins including fornication ( Zina ), but after fornication, you regret it and you always worry about it and you cry about your mistake that you have committed an illegal sin, will Allah forgive?

Indeed Allah forgives Zina if one offers sincere repentance. Prophet Muhammad (ﷺ) said: “The one who repents from sin is like the one who did not sin.” Allah says :

"They are those who do not invoke any other god besides Allah, nor take a human life made sacred by Allah except with ˹legal˺ right, nor commit fornication. And whoever does ˹any of˺ this will face the penalty. Their punishment will be multiplied on the Day of Judgment, and they will remain in it forever, in disgrace. As for those who repent, believe, and do good deeds, they are the ones whose evil deeds Allah will change into good deeds. For Allah is All-Forgiving, Most Merciful." ( Surah Furqan : 69-70 )

Ma, iz b. Malik came to Allah's Apostle (ﷺ) and said to him: Messenger of Allah, purify me, whereupon he (ﷺ) said: "Woe be upon you, go back, ask forgiveness of Allah and turn to Him in repentance."

No doubt that Zina (fornication) is a major sin in Islam and one should keep oneself far away from such sin. However, forgiveness from the Almighty for such a sin is definitely possible, if one sincerely repents by regretting what they have done, and making a firm resolution to never return to such a sin in the future. Allah Almighty states, “O servants of Mine who have acted recklessly against their own selves, do not despair of Allah’s mercy. Surely, Allah will forgive all sins. Surely, He is the One who is the Most-Forgiving, the Very-Merciful.” ( Quran 39:53 ) Once you have repented, it is not necessary to disclose your past sin to others. Our beloved holy Prophet Muhammad (ﷺ) said, "All the sons of Adam are sinners, but the best of sinners are those who repent." (Tirmidhi: 2499)