They might be oil glands - those are often only visible if you stretch the skin.
Do you think that your thighs and anus burning and your testicle symptoms could be anxiety?
Have you had a thorough exam? Since you've had "a lot of sex", it wouldn't hurt to get tested for STDs, just to rule that out, and maybe get a physical exam to make sure everything looks okay. Show the doctor these spots and see what they think.
It's really hard for anyone to diagnose STDs online - they often require lab tests or physical exams to diagnose, and that can't be done online.
Even if it's done just to ease your mind, I think it would be a good idea. Peace of mind is a great thing.