HIV doesn't cause you to bleed from your anus. If you've had diarrhoea and have been consistently wiping yourself as a result then it's quite possible you could cause minor skin abrasions. Straining a lot while defecating can also cause hemorrhoids, which may also cause similar issues. If you are concerned you may have contracted an STI, then you should go to your GP or a sexual health clinic to be tested.
It takes like 30 seconds to google this and read about it on the NHS website, incidentally.
Furthermore, HIV is not a death sentence these days, with many people living completely normal lives with an undetectable viral load that is controlled by various medications. Suggesting that it is cause to be "scared for your life" merely contributes to persistent stigma against people living with HIV or suffering from AIDS.
Also asking for medical advice on a public forum is extremely foolish, since the only people who are qualified to offer it will not do so due to the ethical issues involved in offering advice to a patient without full access to their medical history and without being able to perform a physical exam etc if needed, as well as to cover themselves from potential malpractice suits. Calling 111 is free, as is seeing your GP or visiting a sexual health clinic.