Oh, I'm so, so sorry
Big dragon hugs. There's no such thing as it being "just" a cat, or "just" any other pet. Pets are supposed to be companions, part of the family, etc, not "less than" in any way - anyone who doesn't think losing one is a big deal has clearly never properly (if at all) had one. It's a darn good thing that my leopard gecko died on a Saturday when I was in college, because for the rest of that day and all of Sunday, I was pretty much incapable of doing anything but crying - she'd been my only companion for all of college, the one thing that was constant, the one who I could share my life with and would never judge me, and losing her was devastating. I still can't even look at the baby leopard geckos in pet stores without tears coming to my eyes. So I completely understand how you're feeling right now. While you may never stop missing your kitty, there will come a time sooner or later when you can remember the good times you had with her and smile. Sending you more big dragon hugs, and please, don't feel embarrassed or ashamed to take as long as you need to grieve 
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Yet in my new wildness and freedom I almost welcome the bitterness of alienage. For although nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men.
-H. P. Lovecraft, "The Outsider"