if you are doing just cardio it wont work to loose weight, be on low carbs, 70-80 grams per day , follow diet without diet it wont be possible, research on it . there are many sites search it.
http://www.bodybuilding.com/fun/find-a-plan.html it may help you
Start with warrior diet or intermittent fasting. The best part of it is you can have ur favorite food items too. I had personally lost 7.5 kgs in 1.5 months. Go research on it!
Muscles are becoming bigger so also heavy . Try to sretch before and after exercicing and massages too.