Mysterious weight gain... please help!

I'm a moderately active (a lot of dance, yoga, and going to the gym 3+ times a week) and I have been maintaining a healthy diet but it seems that over the past month I've gained 5 pounds.  I haven't changed anything in the way I've been eating, I just got my period and now that it's over I'm seeing that it's clearly not water weight.  Have I grown? It could be muscle mass - I feel stronger but also slower.  And if I was doing the same activity in the fall why have I suddenly now gained muscle?  I'm not sure what to do, every time I get on the scale it's going up... please help!!

It's possible to gain weight on a healthy diet if you're routinely eating more than you need.  The way to determine if you're simply eating too much is to keep a food diary for a week or so and count the calories.  The CC food log is a good resource for that.  Any extra energy you've taken in will be converted to a combination of fat and muscle if you're very active.

You don't mention your age...  If you were a teen, for example, it's possible that your body is taking the healthy diet and exercise and growing... 

since you work out quite a bit you could have possibly gained muscle!

I have had exactly the same problem over the last few days! Its so random, i put on like 4 pounds when i'm not doing ANYTHING different, except drinking alot of protein shakes and doing a bit more intense weight training... so i'm hoping its muscle, although i am quite skeptical about that. I'm trying not to worry though, and hopefully it'll even itself out again in afew days.