The condition you have is nothing but fungal infection
of groin region called tenia cruris. This is caused by fungi called dermatophytes. This condition is characterised by intense itching red patches which spread as you scratch.
My advise to you is consult your dermatologist
for an antifungal cream and therapy. You have mentioned that you have had these episodes many times, so I suggest you also take a full course of anti fungal therapy also to avoid recurrence.
You should also keep these areas clean and dry to avoid repeated infection. I would also suggest some weight loss
and toning exercises as I am assuming that you might be on the heavier side.