Read this for better alternatives to SoftwareSerial, connection advice, along with some other troubleshooting tips. I suspect that the GPS is not connected correctly.
I would suggest connecting the GPS TX pin to the Arduino pin 8 so you can use AltSoftSerial. It is available from the Arduino Library Manager, under the IDE menu Sketch -> Include Library -> Manage Libraries.
Do not connect anything to the GPS RX pin until you read the connection advice above. The NEO-6M is a 3.3V device, and can be damaged by connecting a 5V Arduino transmit pin to the GPS RX pin.
The above pages are from my NeoGPS library. It is smaller, faster, more accurate and more reliable than all other GPS libraries. It is also available from the Library Manager..