Assalamu Alaikum Wa Rahmatullahi Wa Barakatuhu!!! Masha'Allah akhi it's a good starting point by first seeking advice. Keep hold of that guilty conscience and Insha'Allah do a sincere Tawbah.
Truly, Allah loves those who turn unto Him in repentance and loves those who purify themselves (by taking a bath and cleaning and washing thoroughly their private parts, bodies, for their prayers, etc.)
(Qur'an Surah Al-Baqarah 2 Ayah 222)
Say: "O 'Ibadi (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.
(Qur'an Surah 39 Az-Zumar Ayah 53)
You also have to do a lot of righteous deeds, such as prayer, reading Qur’an and fasting, so as to strengthen your faith and piety. Good deeds erase bad deeds and sincere repentance erases that which came before it, and turns bad deeds into good deeds.
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.
(Qur'an Surah 25 Al-Furqan Ayah 70)
Cut off any interaction making situation worst because it's dangerous.
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).
(Qur'an Surah 17 Al-Isra Ayah 32)
Be careful warning one thing leads to another what you've already done is bad. It may lead to even more disaster if you still communicating with her. Don't let the shaitan fool you.
Abu Hurairah (ra) reported the Messenger of Allah (saw) said, "Allah fixed the very portion of zina which a man will indulge in. There would be no escape from it. The zina of the eye is the lustful look and the zina of the ears is listening to voluptuous (song or talk) and the zina of the tongue is licentious speech and the zina of the hand is the lustful grip (embrace) and the zina of the feet is to walk (to the place) where he intends to commit zina and the heart yearns and desires which he may or may not put into effect.
(Sahih Muslim 2658 Book 46, Hadith 33)
Don't worry about her focus onto strengthen your Emaan and changing your whole lifestyle better.
Then when they are about to fulfil their term appointed, either take them back in a good manner or part with them in a good manner. And take for witness two just persons from among you (Muslims). And establish the witness for Allah. That will be an admonition given to him who believes in Allah and the Last Day. And whosoever fears Allah and keeps his duty to Him, He will make a way for him to get out (from every difficulty).
(Qur'an Surah 65 At-Talaq Ayah 2)
Ibn al-Qayyim (rahimahullah) said "If love develops for a reason that is not haram, a person cannot be blamed for that, such as one who loves his wife or his slave woman, then he leaves her but that love remains and does not leave him. He is not to be blamed for that. The same applies if he glances accidentally then looks away, but love may settle in his heart without him wanting it to. But he has to ward it off and look away."
This does not mean that it is haram for a man or woman to like a specific person whom he or she chooses to be a spouse, and feel love for that person and want to marry them if possible. Love has to do with the heart, and it may appear in a person’s heart for reasons known or unknown. But if it is because of mixing or looking or haram conversations, then it is also haram. If it is because of previous acquaintance, being related or because of hearing about that person, and one cannot ward it off, then there is nothing wrong with that love, so long as one adheres to the sacred limits set by Allah.
Shaykh Ibn ‘Uthaymeen (rahimahullah) said "A person may hear that a woman is of good character and virtuous and knowledgeable, so he may want to marry her. Or a woman may hear that a man is of good character and virtuous and knowledgeable and religiously committed, so she may want to marry him. But contact between the two who admire one another in ways that are not Islamically acceptable is the problem, which leads to disastrous consequences. In this case it is not permissible for the man to get in touch with the woman or for the woman to get in touch with the man, and say that he wants to marry her. Rather he should tell her wali (guardian) that he wants to marry her, or she should tell her wali that she wants to marry him, as Umar (ra) did when he offered his daughter Hafsah in marriage to Abu Bakr and ‘Uthmaan (ra). But if the woman contacts the man directly, this is what leads to fitna (temptation)."