Honestly, the administration does have some fault here. CAS should have been completed by...February at least, and they should have been hounding you for it. While it is your fault for not going through it earlier, you're going to have to ENSURE that your CAS coordinator allows you to receive the Diploma after you complete the CAS hours. I have a feeling the coodinator is not good in the first place, so that's why I'm expressing this opinion.
Yes, focus on your exams and good luck! And if you want to go to uni this September...there is an...um, another method of passing CAS. :P