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, sallallaahu 'alayhi wa sallam, is His slave and Messenger.
You did well by repenting of Zina (fornication). We ask Allah, The Exalted, to safeguard you for the rest of your life and protect you from temptation. We urge you to beware of all the means that may lead to falling into any unlawful sexual relation, such as looking at what is forbidden, being alone with a marriageable woman, prohibited intermixing with the opposite sex, and the like.
An illegitimate child is not attributable to the male perpetrator of Zina; rather, he is attributed to his mother. So he is not to be traced back to you, and you are not obliged to provide for him. What you did, though, of supporting him financially is commendable because it is considered good-doing; Allah, The Exalted, Says (what means): {…and Allah loves the doers of good.} [Quran 3:134]
If you call him to Islam and strive to guide him to it, then this is among the greatest acts of good-doing and most virtuous deeds that draw you closer to Allah, The Exalted.
In an authentic Hadeeth narrated on the authority of Sahl As-Saa‘idi the Prophet said to ‘Ali before dispatching him to Khaybar: “...Thereafter, invite them to Islam and inform them of their duties towards Allah in Islam. By Allah, if one man is guided through you, it will be better for you than having red camels (a very expensive breed of camels considered the most valuable property in the sight of Arabs).” [Al-Bukhari and Muslim]
Allah knows best.