Why am I gaining weight?

I have gymnastics 3 hours a day, 4 times a week, as I've had for the last 3 years. The only difference is we've started doing yoga one saturday a month and we stepped up our conditioning slightly with the approach of nationals and such. Because of this, I've started eating a little more, key word LITTLE, and it's not always the healthiest foods, but I've never been the healthiest eater, per se. I've ALWAYS stayed lean and toned, though. Recently, I've noticed my stomach getting a little softer and my thighs getting less toned, and even my face filling out a bit. Also, I'm about 4 pounds heavier. I don't weigh myself often, but every few weeks or so. I don't understand why I'm gaining weight now, when I've just started training harder..Could it be that little bit of extra food? Orr?