1. first and foremostly the itching during the menstrual flow may be normal due to the endometrial denudation and immunological factors.
2.concern with the mentioning of lymph
3.Actually lymph nodes will appear in the groin region due the genital tract infection
3.is the sexual practice without protection then it should be worry some
4 The way of your description it looks abscess
,visit gynaecologist and take advice.