bestfriend purpose me but issue how i behave i forgot this

I recently said yes when my best friend asked me to be his girlfriend, but now I feel confused about how to act in this new situation. I am naturally an outgoing person, yet I am not someone who can talk to the same person every day or stay connected all the time. After spending hours outside or socializing, I need time completely to myself to recharge and feel normal again. Because of this habit, I sometimes leave messages on seen, which makes him think I am not interested, even though that’s not true. I care about him, but I also need my personal space, and I don’t know how to balance both. This makes me feel guilty, like I am doing something wrong. Maybe I struggle to get too close because of fear of losing someone or being hurt, and that makes it harder for me to open up fully.