Sexually Transmitted Infections can only be caught and transferred through the act of unprotected sex with someone who currently has one themselves. You cannot get them from being unclean. If you think you may have one from unprotected sexual activity, it’s best to get tested.
FAQs

In the UK, the age of sexual consent is 16 years old.
A lot of the time, you may not have any symptoms if you do have an STI, which is why it is important to get checked out if you’ve recently had unprotected sex.
By law, you do not need to tell your partner if you have an STI, it is always best that you do so they can be protected and take necessary precautions when having sex.
Yes, this is not a safe form of contraception. Ensuring you wear a condom will prevent pregnancy as well as protect you from STIs.
You should never have sex if you don’t want to and no one should force you into having sex. If you really cannot say the word no, say you are not feeling well and you need to go home. If you are worried then speak to someone about what happened. Talk to a professional if you are worried it will happen again.