Tennis vs muscle??

well first of all you cant gain that many muscles in just two weeks (and its just a pound difference) unless you were playing straight for hours non stop. im 16 and i play tennis everyday or at least every other day for 2-3 hours non stop. i gained 6 pounds of muscle in 4 months. i suggest that you just keep playing and always stretch before and after you play(it makes your muscles more flexible, prevents injury, and also makes it easier to build). also eat lots of carbs and protein like bread and meat after you play. to give yourself more energy eat 2 bananas every morning or before a game. hope this helps and good luck! oh yeah and try switching things up like playing tennis one day then running or soccer the next. believe it or not but Frisbee is a good activity for helping ur flexibility in tennis