What is the ruling on constantly thinking about and becoming attached to a non-Muslim, and what is the solution to this problem?

Legally, it is forbidden for a woman to have a relationship with a foreign (non-mahram) man, especially if he is not a Muslim, and it is not permissible to marry him as long as he remains in his disbelief. You must repent and distance yourself from everything that leads to communication with him, for Allah has warned against following the footsteps of Satan: "O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins immorality and wrongdoing." [Quran 24:21]. You can request to change your work group to distance yourself from him, and if he proposes marriage, explain to him that it is forbidden unless he embraces Islam.