Hi and welcome to the site. My name is Dr. C. and I'll be providing medical information for you today.
This sounds very much like sebaceous cysts.
There are glands all over you body. This is why it keeps changing places,
A person can get sebaceous cysts anywhere there is skin.
The best thing to prevent sebaceous cysts is to take hot showers and baths often.
Especially after working out or having sex.
Anytime there is increased sweating that then dries on the skin, it's possible for the gland pore openings to get clogged with dead skin and bacteria.
Hot showers and baths unclog the pores of the glands in the skin.
This isn't a serious medical condition but it can be annoying and frustrating.
In some cases more medical treatment is needed.
Antibacterial scrubs and medications can be used in situations where the hot showers and baths aren't enough to fix the issue.
Please REPLY if I can clarify anything or provide more information.