Hallow Dear,
I have gone through your history.
Your symptoms of burning at the anus, particularly during and after defecation suggests that you might have caught some infection - mostly
fungal infection.
May I inform you that
gonorrhoea,
syphilis and HIV are not the only sexually transmitted infections. There are more than 20 sexually transmitted infections which include fungal infections also. Are you sure, all three of you are not having any of them?
The other reason for such symptom could be local trauma like
contusion. Can you tell me what type of intercourse you had? - vaginal, oral, anal or all types? With harsh anal intercourse, perianal tissues and skin may get contused and can give such symptoms.
For fungal infection, you may apply antifungal ointment locally after shaving the parts; however, all three of you will have to take the treatment simultaneously. Please report to the
STD specialist for proper diagnosis and treatment. Please do not waste time, otherwise the lesion will go on spreading all over.
Please, all three of you visit the STD specialist.
I hope I have guided you properly.