...this is driving me NUTS!!

I've lost steadily for the last 4-5 weeks following Weight Watchers. This past week I finally got into a groove with my workouts (they were pretty much non-existent before, I'll admit). I'm now going 3 times a week; either cardio-funk or Zumba at the gym.
But this week, I gained 1.2 lbs.
My husband insists that it just me gaining muscle weight, but I'm not buying it.
I'm really trying not to feel discouraged here...has anyone else had something similar happen to them when they first started truly working out again?