Discouraged

It's been a month now since I joined the YMCA and started swimming. I know that exercise is beneficial even if it doesn't promote weight loss. But really, gaining 6 pounds in a month is quite discouraging. And yes, I know that muscle weighs more than fat but this is rediculous! It makes a person want to give up on exercise. For a whole year I did very little exercise, pretty much ate what I wanted and stayed the same weight. Now in one month, swimming half an hour, three times a week I gain not just a couple pounds but SIX!! It's not fair!!! I just want to cry. But I'm not going to quit because I do enjoy swimming. I guess I'll just have to give up the food.