No matter how old you are, it can be hard to stand up to peer pressure. The important thing to remember is that your friends will understand and respect you if you make a decision that is right for you, even if it's not a popular decision.
It's ESPECIALLY important that your partner respects your decisions (and that you respect their decisions) as well, whether it's waiting to have sex or making sure you practice safer sex each and every time. A healthy relationship is one where both partners trust each other, feel supported, feel physically and emotionally safe together, communicate with honesty, and appreciate each other.
Whether or not you are in a committed, healthy relationship, however, consent is something you MUST understand. Consent means, "to agree to do something or give permission." When we talk about consenting to sex, it means that a person is actively agreeing to have sex with another other person. Consent must be given by both partners each and every time a couple has sex. Even if both partners give consent initially, either partner has the right to change their mind at any point. If someone does not give active consent, you CANNOT assume they are consenting to sex - especially if they have been drinking, doing drugs, or are too young to consent.
Pressuring or feeling pressured to have sex is sexual coercion, a form of abuse. If you or someone you know feels pressured to have sex against their will, there are resources available to make sure you (or your friend) stay safe.
Healthy relationships are all about respect, communication, and honesty. True friends and any partner worth your time will respect you for staying true to yourself.