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 is His slave and Messenger.
First of all, we congratulate you on the great blessing of embracing Islam. This is really a great blessing, and we ask Allah to preserve it for you and make you firm and steadfast on it until you die. We advise you to seek beneficial knowledge, perform good deeds, and befriend righteous and pious women, as these are the best things that help a Muslim woman remain steadfast on her religion.
In regard to your question, it includes some unclear matters, so it is difficult for us to issue a ruling on whether or not this marriage is valid, as we do not know whether this marriage took place before you embraced Islam or after. It the marriage took place before you embraced Islam, then were you following one of the religions of the People of the Book or not [i.e. were you a Christian or a Jew] at that time? A Muslim man is permitted to marry a woman from the People of the Book, but he is not permitted to marry a woman who is following other religions than these two religions, and his marriage to her is not valid.
So it is better to orally ask the scholars in your country so that they may ask you about some details and then give you an appropriate ruling accordingly.
Nonetheless, we can remind you here – for benefit – that the valid marriage has some conditions, the most important of which is the presence and consent of the bride's guardian, and the presence of two witnesses. For more details on these conditions, please refer to fatwa 83629.
If the marriage is one about which there is a difference of opinion regarding its invalidity, such as a marriage without a guardian, then the rulings of a valid marriage apply to it; for example, the woman is not permitted to marry another man unless this marriage is annulled or divorce takes place. For more benefit, please refer to fatwas 92478 and 195979.
It should be noted that the husband must fulfill the rights of his wife; he must provide for her, treat her kindly, have intimate relations with her, and so forth. He must not leave her hanging – neither married nor divorced. All this is injustice about which the husband will be questioned before Allah on the Day of Judgment.
Abdullah ibn 'Amr said, “The Prophet said, ‘It is enough sin for a person not to provide for his dependents.’” [Abu Daawood].
It is regrettable that a Muslim does not adhere to the teachings of his religion, by which he achieves happiness in this worldly life and the Hereafter.
Allah says (what means): {And if there should come to you guidance from Me – then whoever follows My guidance will neither go astray [in the world] nor suffer [in the Hereafter]. And whoever turns away from My remembrance – indeed, he will have a depressed life, and We will gather him on the Day of Resurrection blind.} [Quran 20:123-124]
Allah knows best.