Hi, welcome to the ehealth forum and I am glad to help you.
You seem to be concerned if the sexual exposure in a gay relationship you had 4 years before might have caused HIV infection and the symptoms of intermittent diarrhea and lethargy you are having now 4 years after are due to the same.
You have also mentioned that you have tested negative for HIV, HEP. B and C.
Anal sex in a gay relationship has a higher risk of HIV transmission than the vaginal sex but if the result is negative even 4 years after the exposure, it is unlikely that your symptoms are due to HIV as HIV tests are highly sensitive.
But as you have mentioned other high risk behaviours such as substance abuse and if you have had a repeated exposure recently, you might be in the window period ad you might get yourself tested again 3 months later to rule out HIV infection.
You must consult your personal physician for definitive diagnosis as the same is not possible online.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.