My condolences on the loss of Tigger! The more we love, the greater the pain. Your comment about the empty windowsill really hit home with me! Their passing leaves such a raw, open wound in the heart.
I hope that you are able to find a new kitty just as soon as you are ready. With kitten season just starting, that probably wont be much of a problem. You might want to try putting up an index card at the local feedstores - often pregnant cats get dumped near farms, and the farmers are too busy, esp. as spring starts, to be worrying about the different ways to handle the situation. Knowing that you could give a kitty a home could propose an option. After you feel better, you could try doing research online to plan ahead for your next cat(s) to help you realize that time does heal and that in your future there is plenty more of the special love & affection that cats give. And be prepared - I've been neck deep in grief before, and too miserable to even consider another cat, when, voila! - a cat in dire need lands smack dab in my path. No, they don't replace Tigger, but they need you just as she did; and they will love you in their own special way. I will keep you in my hearts & prayers, Susan