Hey! Welcome to
TH 
Puberty in guys can begin anytime from about 10 to 15 or 16. 12 or 13 happens to be about the average, but it can certainly happen earlier or later.
So, there are a couple options here:
1. Just wait for a while and see if you develop any signs of puberty.
2. If you're particularly concerned about this (which it sounds like you are), then I really do think it is important to talk with your mom and get an appointment scheduled to see a doctor. The doctor will give you a physical exam to assess your development, and might order lab tests to check your hormonal levels.
I know that the prospect of discussing this with others is probably embarrassing and scary for you. I just want to reassure you that it's perfectly normal to have questions about your body and your health, and you're doing the right thing by
addressing them. There's probably nothing to be very concerned about at this point, but it's a really good idea to get everything checked out
