7 lb weight gain in 2 weeks??

gigantan

Since I became pregnant, I have been monitoring my weight gain and have been doing well (gained 4lbs in first trimester, by week 20 gained total of 8lbs). I am at 22 weeks, and the scale tipped at a total of 15lbs!  I don't think I have been eating differently and my activity level is the same (exercise 2-3 times a week). 

 Does anyone else have weight fluctuations like this?  I am not so worried about the total weight gain as much as I am about the amount gained in a two week period of time.