So sorry to hear about Oliver. When you posted about him a while back, I was experiencing the same thing with my Ditto, who did not make it. I still miss him too. Just remember that you gave Oliver all the love you could and that made him a very special cat who led a happy life. Oliver was a beautiful cat with a sweet face and apparently a personality to match or you would not have loved him so. Don't be ashamed of the tears; they honor the love you felt for one of God's creatures.
You did the right thing and it is okay to grieve, it is natural and healthy. In time, it will get easier; there is no rush. This is the one place in the whole world where most everyone understands how you feel, so vent away. Here is a big HUG for you.