Please, post the picture of your MPU6050 Breakout Board Module. After that I will forward to you diagnostic sketch; where, the we will be able to see message if the Sensor has been detected at address 0x68 or not.
Where have you connected the AD0-pin of the module? It should be connected at GND-pin to select I2C address at 0x68 and at 5V to select address 0x69. Reemmeber that the MPU6050.h Library has keyed the address 0x68.