Rapid Weight Gain

shortstack4444

I am currently 25 weeks and over the last two weeks I have put on 6 lbs for a total of 9 lbs this month?  Up until 21 weeks I had only put on 9 lbs and it makes me nervous to have doubled my weight gain so quickly.  I am still exercising (walking 5-6 days a week and 20 min of pilates 3-4 days a week).  I have noticed an increase in appetite however I have been making healthy decisions so I do not feel there has been a big increase in calories.  Has anyone experienced this?  Or do you have any recommendations on how to control this?  I am only 5'0" and am really trying to stay within the proper guidelines for weight gain (or at least as close as possible).