Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Any personal relations between a man and a woman other than the marriage boundaries are forbidden regardless of the means whether it is done through Internet or else. It is also not allowed even if the purpose is to get married. Hence, you should ask forgiveness of Allah and return towards Him. For more details in this subject read the Fatwa: 84281 and 81668.
It is desirable for a woman intending marriage to choose a pious, God fearing and noble man. Because, weakness in religion, not fearing Allah, and looseness in following Shariah lead to disorders in a married life in particular and in the life of Ummah in general. The Prophet (Sallallahu Alaihi wa Sallam) said: “If a man proposes a girl, had you like his religion and character, you should marry her to him, if you do not do so, there will be trouble and deprivation."
It seems to us that this man does not achieve the aforementioned characters. If he were so he would never continue having such illegal relation with you since three years. On this basis we apprehend that marriage to him may cause many problems. In addition, these youth, generally speaking, are not serious in marrying a certain girl rather they use the promise of marriage only to entrap girls to fulfill their desires or to gain some mundane benefits such as to travel to some countries where they cannot enter except through having personal relations with girls.
Therefore, you have to submit yourself to the decision of your parents since their decision is most correct. Also know that it is not allowed for you to marry without their permission. The Prophet (Sallallahu Alaihi wa Sallam) said: "Any woman, who gets married without the consent of her Waly, her marriage is invalid, her marriage is invalid, her marriage is invalid." [Narrated by Abu Dawood and al-Tirmizi].
Allah knows best.