It's true that muscle is more dense--however, 2 weeks is not enough time to gain 5 lbs of muscle! So... I'd say you need to track those calories and portions. Don't just guess at it--too easy to underestimate that way. It's amazing how many calories some foods contain--foods we never even think about. For example, a serving size of Doritos is eleven (11) chips and contains 140 calories. When was the last time you counted out the chips?
FitDay (and probably some other tools as well) allows you to estimate what your body burns in a day just being alive, plus any additional activities. A good rule of thumb is to subtract 500 cals from that number, and that's your target for eating. That will also give you an average loss of 1 pound a week, if the numbers are accurate. (Sometimes they aren't and need to be adjusted.)
Don't get discouraged! Keep working it!
Jay