Right off the top of my head you must have done something wrong.
I say this because I always prime with 1 1/4 to 1 1/2 C DME and NEVER have gushers.
Since you have gushers and used the proper priming amount I can only surmise that you bottled early.
Several questions come to mind:
1. What was your OG and FG?
2. At what temp did you let your primed bottles sit for those 2 weeks?
3. Did you disturb them in any way?
4. Do you know how to pour a Hefe Weizen?
Answer these and I may be able to help you.