Praise be to Allah.
We ask Allah to guide you and accept your repentance.
We advise you not to tell your husband about this matter and strive to repent from it and give it up.
Always bear in mind that Allah is watching you and can see what you are doing at all times. This is most likely to make you feel shy before Him and venerate Him.
You should always remember death and the Hereafter and the Reckoning. If a person remembers death a great deal he will inevitably prepare for it by doing righteous deeds and repenting from sin.
Cut off all ties with this girl immediately. If you can move from that job, that is essential. Continuing the relationship between you means that there is no repentance and that the sin will continue.
Rather we tell you: if you can move from that city altogether, then do that and do not hesitate.
There is no remedy for this disease except keeping away from that girl altogether.
As for your prayer being accepted, that is up to Allah, but be wary of giving up prayer; rather you should strive to do a great deal of it and to read Qur'aan, in the hope that this may be a means of Allah accepting your repentance and guiding you.
Listen to lectures and exhortations by well-known scholars and daa’iyahs who are known for their trustworthiness, religious commitment, sincerity and knowledge. Think about how Allah is forbearing towards you. How can He be forbearing when you are persisting in disobeying Him? If He so willed, He could punish you for this sin and you would have a bad end. Think about how Allah has concealed your sin. What would you do if your husband and other people found out what you are doing; it would be a big scandal. How would your life be after that? So hasten to repent before Allah hastens your death or punishment, in which case regret would be to no avail.
The gate of repentance is open and Allah accepts the repentant slave and rejoices over him; He forgives him and accepts his repentance no matter what his sin. The one who repent from sin is like one who did not sin at all.
We ask Allah to guide you.