Hi there, my best advice would be first calm down and take a moment to breathe. Everyone has ups and downs and sometimes those "downs" really have the worst timings.
I would suggest work hard for you mocks in September and if your confident about getting an A in sociology and Bs in your other subjects with the right amount of work put in then don't hesitate to do it. More importantly don't worry about how your teacher or parents or friends may react to that just remember that you did the best you could and your grades are the result of that.
Moreover, You still have year 13 so make sure you don't slack of there and work super hard and your actual grades will meet your predicted grades they may even be higher.
Don't stress and go for it.