Muscles are becoming bigger so also heavy . Try to sretch before and after exercicing and massages too.
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!
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