Lonegamer- your in a tricky situation. It totally boils down to you deciding according to your wider circumstances!

If I was you and just advising based on the limited info you've shared with us, I would have gone for the MS. You do not get such opportunities everyday, plus it will help you immensely in your career. CSS like I say is not black and white, you should not consider it as a matter of life and death! If Allah has willed it for you , then nothing can stop it from coming to you. Consider CSS as another career option and sit the one attempt after your masters. If you pass, well and good. If not, then at least you have your masters to fall back on and pursue something further out of it.