The problem with my weight!!!

Went to the nurse in my doctors surgery last week. I go there once a month to get weighed, and have my blood pressure checked as part of a weight management programme.
I have been going for around eighteen months, and have had some success, managing to shed three stone. I have gone from an obese B****** to merely a fat B******!!!
This last month i have really tried hard. I walk about six miles a day in work, take the dog out for a two mile walk at least once a day, have hit the gym at least three times a week in the last month, and swam at least one and a half miles a week.
I expected to lose several pounds, indeed I looked and felt thinner. Imagine my surprise when the nurse told me I had put on four pounds!! The nurse told me not to be too despondent,as my exercise regime had probably turned fat into muscle, which weighs more.
Better luck next month!!!