I've been working out a ton and eating healthy, why am I gaining weight?

So for over a month now I've been eating healthy foods like grains and fruit and taking in about 2000 calories a day. I found that my basal metabolic rate is 1990. On top of that I've been biking for about 1 hour every day and walking around 3 hrs a day. Somehow I've gained weight! I doubt it is overeating, because months ago I ate tons of junk food and drank sugary drinks, with minimal exercise. My weight stayed the same then, but now I've been working hard and have gained around 5-7 pounds in two weeks! What is wrong with me!!!