Using a condom is the cheapest and most effective way to protect yourself and others from HIV. You should always use a condom whilst having anal, vaginal and oral sex. This will protect against HIV as well as other STIs.
You should not inject drugs, but if you do, then use sterile injecting equipment and do not share injecting equipment. Bristol Drugs Project offer free needle exchange programmes.
Post Exposure Prophylaxis or PEP can help protect you if you feel there is a risk that you have contracted HIV. This is a strong course of medication that stops the HIV virus taking hold in your body. You can get this treatment on the NHS through your GP. You must start taking the medication less that 72 hours after exposure in order for the medication to be effective.
Pre-exposure Prophylaxis or PrEP is a course of HIV medication that can be taken before sex to prevent HIV infection. It is very effective if taken properly. While PrEP is currently unavailable on the NHS, you can purchase it online. The website https://www.iwantprepnow.co.uk/ offers advice on using PrEP, as well as ways to buy PrEP and advice on how to manage your health whilst taking PrEP.