Pus filled pimples on lower body & butt.

Pus-filled pimples on buttocks and lower body. The pimples start small and itchy, then become big, red, and painful with a white dot-like on top. They are deep, big, and hard inside than outside and after a few days, they burst and release water, blood, and pus. The area is painful and experiences pain in the whole area till the depth of pimple The pimples have been occurring for more than a month and they keep coming one after another, like one ends and other occurs, it doesn't occur all along they occur one by one and one after another They  are mainly on the back buttocks and occasionally on the outer thighs. It started from the outer thigh area right above my knee and left big black mark The pimples are both painful and itchy. There are no other accompanying symptoms. The severity of the pimples is 9 out of 10 There is no fever, chills.