Pair my Apple Watch back to my iPhone My iPhone and Apple Watch were paired but the iPhone went in for repairs. 

On return, the pairing to my Watch was broken. Now I want to re-pair the Watch without losing my exercise data gathered for past 2 weeks. 

How can I pair these two devices without losing my exercise data?
Your Apple Watch will only upload that data to the paired iPhone. Check whether the watch shows up in the "Watch" app on your iPhone. If it does, you may be able to get them talking again by going to the Bluetooth settings, tapping the "circle i" and connecting the watch again. If so, they will sync and all is well.

If not, retrieving your last 2 weeks of data is not possible since pairing with another phone will cause the loss of the data on the phone.