Boarding School ?

Okay so I'm in year 11 now and I'm at an all girls day private school and I'm all set to move to a mixed boarding school in September to pursue my sport which I'm very talented at and enjoy at lot, and I had made my mind up completely and was so set on going, as I just hated my current school so much. I have loads of friends there and I'm popular and also really enjoy the social side because I go to all the parties and stuff aha, but I just hated the way the school was run and the academic pressure I was under, and the school no longer has anything o offer me anymore so I felt it was time to move on. However suddenly over the last week I've felt beyond overwhelmed and have literally completely changed my mind, I don't want to board anymore and the thought of being away from home (even though I'm 16...) completely petrifies me, and I'm so confused because going to this school is literally everything I've always wanted and I'll have so many amazing opportunities but now I don't know what I want to do I'd rather just stay at home and just put up with my school for two more years. The down side is doing that will completely destroy all my sport. Can anyone offer any advice on support in what to do here, I know it's very hard to do so as ultimately it's me who must make the decision and be happy with it but I'm it's so lost and confused, and I have to let school know by next week, and I'm also in the middle of my GCSEs so I'm just finding it all a bit too much at the moment I guess😂😭 Also my sister is moving to a big school in London, which also just messed up the whole situation even more, and my parents won't let me discuss the move with a single person so I can't even talk to a friend about it thanks x
(Sorry I don't know if this posted the first time)