@megancoleman08,
Yes, Megan, at 5'10' you are an Amazon- OWN IT! Stand tall and make the world respect you for it. I know it can't be easy when you are only on the cusp of 14, but with your face and height you could be a supermodel by the time you turn 18, or at least a warrior princess. I know you are at an awkward stage right now - transitioning from child to young woman is not easy, no matter what your size. Yeah, boys might give you a tough time, but that's because they are boys and insecure about their own bodies. Men will be falling at your feet in a few years (don't rush it, it brings a whole mess of different problems).
I wouldn't recommend running. It might help you lose weight, but it's not going to tone your upper body - plus it's a big bore and hard on the knees. Any chance you could convince your parents to take you to see a professional trainer at a local gym or find a pilates class? I think at your age you need to have someone who really understands anatomy to give you advice about the best way to exercise. It's hard to learn proper body placement and control on your own. You would probably benefit from some strength training, as well as body sculpting. Much of this requires specially designed equipment and some guidance. Maybe you could get your mom to join a gym with you and take classes together.
In the meantime, the best exercise is fast walking and some slow, controlled sit ups. I looked around on the web and I didn't see anything I thought was very helpful. Maybe others know better, but I really think you need to take a few classes with a professional. If that can't happen, I assume you have a Phys.Ed department at your school. Go speak to one of the teachers, or even a school nurse, about exercises you can do at home.
If the belly piercing motivates you to meet your goal - well, go for it. Every grown-up here has done stuff like that and we understand the urge to be a little crazy. Most of us have learned from experience rather than advice. It's not fair of me to insist otherwise.
Keep us informed about your progress.