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 it is forbidden in Islam for a woman to establish an affectionate relationship with a marriageable man. Therefore, you are both obliged to repent to Allaah and immediately cut this relationship. Furthermore, it is not permissible for you to converse with him except for a need; you are not permitted to talk with him especially about the matters which you mentioned in the question. For more benefit, please refer to Fatwa 81356.
If we assume that he proposes to marry you but you fear that if he marries you, he will not keep you chaste, then we do not advise you to accept him as a husband and there is nothing which Islamically prevents you from refusing to marry him. In such matters, you should not be dragged by your affections, as this could lead to unpleasant future consequences, like divorce and the like.
It should be noted that a man who is tempted by men has a kind of disease, but if the matter is just restricted to feelings and the person repels his thoughts and keeps himself chaste, then he is not sinful for having these feelings.
Therefore, he should earnestly ask Allaah to repel these thoughts from him, and he is permitted to seek the help of specialist psychiatrists as they may cure him, thanks to Allaah.
For more benefit, please refer to Fataawa 85918 and 83746.
Allaah Knows best.