Sex means different things to different people.
It's totally okay if you aren't ready to have sex. A fancy word you may have heard for this is abstinence—not having sex at all. In reality, not everybody is having sex. Some people including adults live happy and successful lives without having sex. Hard to believe but it's true. If you aren't ready that doesn't mean you don't care about or even love your partner.
In fact, if couples are in a healthy relationship, they will respect each other's decisions. If someone is only in the relationship for the sex, you're honestly better off alone. All good things take time and sex is just the same. If you simply aren't comfortable with the idea of sex, then it's totally fine to say NO!
Good news! There are many ways to show affection to your partner without actually doing it. For example try:
- Leaving nice comments on your boyfriend's/girlfriend's Facebook wall
- Telling them why you love them or want to be in a relationship with them
- Caressing each other. It can be as simple as a back massage, or light kisses on the neck
- Snuggling with them when they are having a bad day
- Mutual masturbation ("handjobs" or "fingering")
- Or any of the other ideas that you can find here