I had very mild genital ulcer, night sweats, fever, itchy sensation inside penis, sore throat, angular chelitis one by one after sex. what can it be?

See your doctor: you may need to be tested for HIV infection or other sexually transmissible infection (STDs).

Can't tell, see doc: Your symptoms don't fit with any one STD -- and maybe none at all. The greatest concern is herpes, if indeed you had a genital ulcer, even if "mild" (by which I assume you mean small, painless, brief, etc). I suggest you stop trying to figure it out online and see a doctor or clinic experienced in STDs and sexual health.