I think I'm having feelings for my best friend and it's really complicated & depressing me. Help?

First of all, we're best friends for a half-year round already but we've known each other or seen each other already in a community we both go into for more than 2 years already I think? It just took us some time to be finally friends more than just strangers around the same community.

We became best friends through a game that we're playing for as long as our friendship is already, we even made more friends and a group of people to play along with. We grew even more closer as we get to know each other and our relationship with our exes, because for some coincidence we're both fresh from break-ups on the same day we get to be friends. Then days, weeks, months pass by; we became somewhat platonically romantic with each other even after our meet-ups. Which this makes me feel like I'm somewhat special or her being special for me. It's so confusing, but I kept silent and went along with the flow. But as days pass by I come to stressing this out lately because she makes me feel anxious, jealous sometimes that she doesn't even mean to.

And just recently, she's kinda distancing herself at me. I don't understand why because she isn't that type... She's open but won't reply to me. Nor seen me, even at the game we loved to play together. She wouldn't play with 'just me' but she'd come to play with me only if we're with the others. It makes me feel so anxious and sad that I don't understand why... we even have so much more plans to do together in the future.

I'm not sure about confessing yet nor for any relationship yet so I just kept silent. But as my best friend? This is making me sad. Why is she doing this? I just don't understand, I think it's better if I just kept myself shut and let her be if she wants to distance herself out.