Yeah yu need to reschdule. The rules are really saying you need to have a HS diploma or similar, if you did not pass it yet since you are awaiting the results you won't be eligible till after and can be denied sine at the time of your interview you didn't have the requirements and they might check your answer on the first application or entery and it could be you filled out you already have your HS diploma, which at that point is not true...so don't go before you have it...you might risk that they run out of GC but getting denied can be worse later on. Try to reschedule for 1 month later, so you don't have to keep rescheduling.
Good Luck