Weight Gain

Megan
I'm currently 22 weeks & today at my routine OB appointment my doctor suggested I start keeping a "food diary." In my first trimester I lost a little weight due to morning sickness, but clearly I've put it back on. Apparently I have gained 10 pounds in the last 5 weeks. Im 5'4 & today I weighed 134 pounds. I'm not a terrible eater -- I eat basically three balanced meals a day & snack on good foods, with an occasional indulgence. I'm so confused where this weight came from because honestly I don't see it anywhere on me (other than a baby bump, obviously). Is this something to be concerned about? Should I make a change to my diet? My OB has me all worried now...