You can care about him, enjoy kissing him and still not want sex. You can also have wanted it before and feel differently today. Finding the words may be awkward; your answer doesn't need to be perfect to count.
Start with what you actually want, then say it as clearly as you can.
Work out what feels comfortable
Are you choosing celibacy, waiting for marriage or simply not ready tonight? Do you want to slow down while you get to know him? Are some kinds of affection welcome and others uncomfortable?
You don't need a detailed explanation. Knowing your own limit can help you avoid agreeing to something just because you're afraid of disappointing him. Ask yourself what you want separately from what you fear might happen if you say no.
Say it plainly
A gentle tone can go with a clear answer. You could say:
- “I'm not ready to have sex. I want us to slow down.”
- “I'd like to be close, but I don't want sex tonight.”
- “I want to keep dating you without having a sexual relationship right now.”
You can acknowledge that he wants something different without apologizing for your decision. Neither person's level of desire needs to become an insult.

Share as much of the reason as you want
An explanation may help him understand you. It isn't something you owe in exchange for respect.
- “I need more time before I feel comfortable with this.”
- “I'm choosing celibacy, and I intend to keep that commitment.”
- “I want to understand where our relationship is going before we have sex.”
- “I care about you, but I don't feel ready.”
If you're still working out your feelings, say that. You can keep private details to yourself. An excuse you don't mean may create another conversation you don't want to have later.
Reassure him only where it's true
If you love him or feel attracted to him, you can say so. You don't have to exaggerate those feelings, promise sex soon or give a date just to soften his disappointment.
Try: “My feelings for you haven't changed. I'm not comfortable taking this step.” If he remains disappointed, you can acknowledge that while keeping the same answer.
Describe the affection you do want
You don't have to offer an alternative. If you'd enjoy something else, be specific:

- “I'd like a cuddle without anything sexual.”
- “I'm happy to kiss, and that's where I want to stop.”
- “Holding hands feels right for me today.”
- “I'd prefer to spend time together without touching right now.”
Agreeing to one activity doesn't mean agreeing to another. You can change your mind and stop, including after something has begun. When he respects a limit, let that response mean that he's listening.
Talk about longer-term expectations
If waiting is a personal commitment, explain what it means for the relationship. Avoid offering a deadline you can't promise or using sex to bargain for a proposal.
You may discover that you want different things. Both of you can discuss compatibility; neither has permission to pressure the other into sex.
Notice how he responds
A sincere question or disappointed feeling can coexist with respect. Repeated pleading, guilt, threats or blackmail are pressure to abandon your answer.
If the discussion keeps circling, a short response may be enough: “I've told you what I want. My decision hasn't changed.” You don't need a fresh reason every time he asks.
If you feel threatened or unsafe, seek support from someone you trust and consider how to leave the situation safely. Finding a warmer phrase won't solve someone else's refusal to accept your boundary.