Muscle weighs more than fat and if you're doing as much as you say you are then you've more than likely developed some good muscles and it's probably just that simple.
Don't get hung up on weight, Brad Pitt was classed as obese when he did the film Troy. I have no idea what I weight, i go by how my clothes feel, eat a balanced diet and I exercise. If you're really worried, talk to a nutrionist or ask for a consult with a trainer at a gym but as I said, the actual weight is the last thing I worry about.