Provided that you have told him you are a believer, you are worried about the wrong thing. It is in no way “leading someone on” to fail to make it a point to tell them you live a life of integrity and are planning to do everything in your power to keep the two of you headed towards Heaven. You told him you are a Christian. You do your best to unfailingly act like one every day in every way. You dress, speak, and act modestly, like a chaste woman. That is enough.
You aren’t worried about telling him you won’t lie for him or to him, right? Not worried about how you’ll tell him that you will never cheat on your taxes, miss Mass on Sundays or Holy Days, blaspheme or tolerate blasphemy, engage in nature worship, covet what someone else has, or any of that? Really–you cannot waste your anxiety over the worry that he is going to say, “When you said you were Christian, I didn’t think you meant it!!” Nothing could be worse for his soul than if you didn’t mean it. If he says, that then, your answer should not be “yes, I’m sorry I didn’t tell you.” Your answer should be, “well, yeeeees…you know I’m Catholic and you know I’ve never ducked anything else about my faith. Why would you expect this to be different?” Honestly, he can’t say he was “lead on” without gravely insulting you. More to the point, I do not know how you imply that he thinks otherwise without insulting him. You may as well ask him if it is safe leaving your purse alone with him while you visit the bathroom! Ask a thief that question, and he’ll lie to you. Ask an honest man, and he’ll be hurt. Get someone in-between who thinks it totally OK to rifle your purse as if it were already community property because it is what all his friends do with their girlfriends, and his feelings would not be what you’d worry about!!
Don’t worry about bringing it up. Keep him in your prayers–you are talking about the concern that he plans to turn both of you over to mortal sin–watch that you do not hide your approval of those who live a moral life, but otherwise, give the situation to the protection of the Holy Spirit. Make St. Joseph, Guardian of virgins, Pillar of families, Terror of Demons, your ally:
Now who is going to harm you if you are enthusiastic for what is good? But even if you should suffer because of righteousness, blessed are you. Do not be afraid or terrified with fear of them, but sanctify Christ as Lord in your hearts. Always be ready to give an explanation to anyone who asks you for a reason for your hope, but do it with gentleness and reverence, keeping your conscience clear, so that, when you are maligned, those who defame your good conduct in Christ may themselves be put to shame. For it is better to suffer for doing good, if that be the will of God, than for doing evil. 1 Pet 3:13-17
