Puppy Itching A Lot Near His Private ?

My 11 week old puppy a shih tzu mix with chihuahua, starting itching and scratching himself a lot lately

thought he might need a bath time, seeing as he hasn't gotten one so i took him a really nice with warm water puppy shampoo bath

yet his still itching a lot near his back end, not his butt, but in between his legs, where his i don't know a proper word to say well his balls are going to be at, he itches and whines while itching himself, don't know whats wrong, has no fleas at all, not ticks, his skin is nice, whitish pinkish color, ive been seeing him scratching himself, lately but now his itching with purpose and whining while doing it,

thought maybe he might need medicated shampoo

was wondering what are some puppy shampoos out there, that are medicated

his a white puppy with brown spots, three big brown spots on his body, two brown spots over each eye and ears, his light tan, with brown, with liver brown color spots, his very cute, looks like a purebred jack russel terrier