kareem613, my experience with DHT22s has shown me that not all are created equal! I use a 4.7K pull-up but it is not always necessary. Nonetheless, I suggest you use one because the non-blocking code is sensitive to the DHT22 data output rise time and the resistor helps. Another thing is the voltage used for the DHT22. I do not suggest powering off the 3.3*v line since it is lower that 3.3V and I have found a lot of DHT22s that will not work at anything even slightly lower than 3.3V.
Try the pull-up and let me know how it goes.