Honey, babies are wonderful, no doubt about it. But you're very, very young. There are other ways to be around babies besides having one yourself.
Babies are a joy but they're also a huge job. It's not all fun and games, snuggling and kissing, dressing them pretty and showing them off.
They need total attention from their parents. That means no Facebook, no movies, no doing whatever you want when you want to do it.
There's colic, teething, colds and flu. Diaper rash and a whole host of other "not so much fun" type of things. Once you're a mom, that baby must come first 100% of the time. At 13, you're not done growing up yourself. Emotionally as well as physically. Your body is still growing and changing. Should you decide to have a baby at your age, it's very possible there could be complications. It could be anything from a miscarriage to hemoraging after the baby is born and in order to save your life, they have to do a hysterectomy. If that happens, you won't ever have another child. That would be incredibly hard to deal with when you love babies so much.
Don't be in such a hurry to grow up. The time will come when you meet your Prince Charming. He'll love you more than life itself and you will have children together and live happily every after.
See about volunteering at a day care, babysit for friends and family. There's some mom out there that would probably LOVE to have some help with her little one(s).
If the maternal instinct is so strong and you really feel you need someone to love and care for, get a puppy.