one of my testicles is larger than the other, and i feel a small, seemingly unattachted ball connected to it somehow.
i did check a few sites that told signs and swelling of one and a lump that caused no pain was another, i'm worried, im 15 years old

Go to the doctor and get checked. It could be any number of things. If it's cancer you want to catch it early.

The fact that one testicle is larger than the other is perfectly normal. However, the fact that you can feel a small, painless lump in your scrotum is troubling.

Get yourself to a doctor ASAP. It's probably harmless, but you've got an early warning sign that definitely needs to be checked out by a pro. You're in the right age range to be at risk for this kind of thing (younger men are at higher risk than older men). It's probably nothing, but if it is something serious, you could save your own life by seeking medical attention now.

See your doctor. Come on now. Do you really expect an online diagnosis?

if your testes arent the same size thats fine
they arent sopoused to be.
and you are too young to have testicular cancer.
But get a checkup at the doctor.
goodluck =)

Best way to know is go to the Doctor, I would be worried if I were you. Those are your jewels man.