Three ways to ease your fears about making a move
Look to buy first
In most markets it is a real mistake to put your home up for sale before you start looking for your new property. Identify the geographic area where you are interested in buying. Even if you don't see anything on Zillow, it doesn't mean you can't or won't find the right home.
Think outside the box
Be proactive! Keep in mind that there are probably many people like you who want to make a move but are afraid as well. Have your real estate agent send a letter to the neighborhoods in the geographic areas where you want to live. The letter should be heartfelt and personal while announcing that you are ready to buy a home in that neighborhood. You could find a home to buy that may not even be currently listed or for sale.
Protect yourself legally
Each state varies in how the purchase process is conducted. Talk to your real estate professional about adding a clause in the purchase contract for the home you are selling that will enable you to not sell the home if you cannot find a suitable home to buy.