What could be my problem?

Over the past 3 months or so, I think I've been gaining some weight without meaning to. My diet has changed considerably: for lunch, instead of having a low-sugar yogurt, a protein granola bar, and something else low carb, I'm having oranges, applesauce, bananas, strawberries, yogurt, etc. Basically, I'm consuming a lot more fruit that I would have 3-4 months ago. For breakfast, instead of having 3 scrambled eggs, I'll have a banana, a protein shake and some low-fat sausages. I'm eating fruit for 2 meals now. I've also gotten into the habit if snacking on dried prunes (no added sugar) raisins, and I'll eat plenty of whole grains. According to the scale, I've gained about 10 pounds. My exercise regimen hasn't changed. I will also mix fruit juice with water and drink it. Lots of fruit. I'll usually have one GNC lean shake a day for breakfast; I didn't used to have them. What is the problem with my diet? I should add that I'm 17 and I'm frequently under stress. I take vitamin Bs, melatonin, and Pion Flower sometimes. My monthly cycles are 7 weeks apart.