Fungal infection or Ring worm...highly itchy.. when occurs in groin it's called Jock itch. Usually fungal infection is common in moist areas of the body like skin folds. It's mostly circular or round in appearance..may be red or black in colour. Treatment depends upon the type and severity. Avoid sharing towels, clothes and soap. Sweating increases it. As it has to be differentiated from eczema and infection, it's a must to see and confirm the diagnosis for proper treatment..So, please send photos of the affected area,  by direct private online consultation for accurate diagnosis and proper treatment.

Probably you Should be suffering from a fungal infection .