Increased & Changed up my exercise, but now gaining?

Ok, so at the beginning of the month I joined a gym and started a new exercise routine. I am taking a new water aerobics class 3 times a week  that is more intense. I also have been using the machines for a half hour after class to work on toning up my arms and legs. (I've been seeing a personal trainer and I have seen him twice so far.) I have also started walking a mile a day for the past couple months. My weight had been fluctuating up and down between 207 and 210, but I weighed myself this morning and I was 212!!! AHHHH!!!!! What is the problem? I admit I have been slacking in my water and protein intake a little, could that be the problem?

I think you are just gaining muscle.  It's frustrating, isn't it?  I'm having the same problem.....

Yes, and I gained more this week!! ARGH!!!! I am flipping out!!!