The area in between my testicles and thighs always is stinks. Any suggestions?

Hygiene. If you haven't showered during the previous 18 hours, it's likely you'll have enough sweat, sebum and perhaps cotamination by semen or feces to have enough bacterial overgrowth to create a strong odor. The cure is better hygiene, perhaps looser-fitting underpants.
Fungus. I would definitely have a physician examine the region, but one of the common sources can be a fungal infection or 'jock itch' which can be relieved with a topical anti fungal like lotrimin (clotrimazole).