why do I have different personalities?

Im so awkward with the people I sit with at lunch but when I hang out with them outside lunch it's like I'm a completely different person. Like I'm more outgoing and really fun to be around with. And when I'm on my track team I'm so shy like i have a hard time talking to people, but when I'm with my tennis team I'm so outgoing it's like total opposite. I have so many different personalities and I don't know why. I like when I'm outgoing and fun I don't like the awkward and weird side of me. Even if I try to not be awkward, it won't work. I try and nothing in still awkward. Why is that?