@raaden89 Simply you can't. Sigfox as very very low downlink ability ( network to your device as 4*8 bytes limits per day!) .
You just can't design this functionnality as is, and you need to think to another way to work.
exemple:wait in your device for a downlink coming from sigfox with a sequencial number index, send after that the gps pos with following index and so on. On the next download your device will receive a new index (or the same at the last time if no uplink as been successfull) and your device will restart to send the gps pos following the index recevied.