Hi bakatsine!
There are three main reasons to feel itchy in your genital area. They are friction, fungus and two rather critters, pubic lice and scabies.
Friction or skin rubbing against skin generates heat and sweat and produces tender, red, itchy patches(physically active or obese are especially susceptible)
Due to intensive itching at night I think you may have your genitals infested with either pubic lice or scabies. The main symptom they're causing is itch that is getting worse at night.
Scabies are microscopic mites that burrow into the skin and infest not only the skin in genital area, but also at other body parts(waist, breasts, armpits, hands)
Pubic lice aren't microscopic. They are size of a full stop and are very visible. You can noticed them as tiny white, light brown or grayish flakes of skin, but they move or you can find oval eggs attached to your body hair. Sometimes their droppings can be seen as black dust on the underwear.
Any close contact with someone who's infested, it doesn't have to be sex, can give them to you(using the same bed linen, clothes, hairbrushes or towels)
After you are exposed to pubic lice or scabies, it may be 2 to 6 weeks before symptoms are evident. Itching and annoying is about all these lice and mites are and the treatment is very simple.
Best wishes!
Marija