All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, you should know that the Mercy of Allaah is so vast and that Allaah forgives every sin whatever great and grave it is. Indeed, Allaah opened the door wide open so that people would repent. Allaah Says (what means): {Say, “O My servants who have transgressed against themselves [by sinning] do not despair of the Mercy of Allaah. Indeed, Allaah forgives all sins. Indeed, it is He Who is the Forgiving, the Merciful.}[Quran 39:53] Allaah accepts the repentance of a non-Muslim, and a hypocrite, how come that He does not accept the repentance of a disobedient Muslim? Therefore, you should take the initiative to repent from every sin and you should not despair from the Mercy of Allaah as being despaired of the Mercy of Allaah is one of the great major sins. Allaah Says (what means): {…and never give up hope of Allaah's Mercy. Certainly no one despairs of Allaah's Mercy, except the people who disbelieve.}[Quran 12:87] For more benefit on the conditions of repentance, please refer to Fataawa 86527 and 87903.
Indeed, among the things that complete your repentance from Zina (fornication or adultery), is to avoid any means that may lead you to commit this sin again, like establishing affectionate relationships, being in seclusion with a non-Mahram man and so forth.
Moreover, none should blame you for a sin which you repented from, and your family is wrong for driving you out of home because of this. By doing so, they are exposing you to evil and are opening a door of temptation for you. So, we advise you to be careful and you should seek the help of some pious and righteous Muslim brothers so that they would talk to your family and ask them to take you back to them.
Indeed, you did well when you refused to abort that fetus because aborting him is killing a soul without any right as we clarified in Fatwa 85930. So, when you give birth, you should be kind to your child and nurture him well (according to Islam). He is your son and he should be traced back to you; he should not be traced back to the fornicator who is not his father at all. If you fear any embarrassment for him [child], then you may give him a general name like Ibn ‘Abdullaah or Ibn ‘Abdur-Rahmaan and the like, as all the people are slaves of Allaah. For more benefit on the ruling on a child born out of wedlock, please refer to Fatwa 85430.
Also, when your waiting period expires by giving birth, then you should take the initiative to marry and it is permissible for a woman to look for a pious husband to marry as we clarified in Fatwa 82471.
As regards the statement of that young man that you are a prostitute, then this is accusing you of Zina and you are permitted to take his matter to the authorities. Besides, how dare he state on behalf of Allaah that you will enter Hellfire? It is not permissible to judge anyone to be a dweller of Paradise or Hellfire except those whom Allaah and His Prophet judged to be so. On the contrary, if you repent, you will not be held accountable for your sin, Allaah willing, and you will be not be punished because of giving birth to this child.
Allaah Knows best.