As you are young and have lot of free time ,I feel that you must be eating a lot and almost no exercise .You have gained 5 kg in 4 months and that to around wait and tummy which is mostly fat and not desirable. You must do aerobic exercises
to burn calories which you take like dancing,runnig,walking,Swiming or cycling all these activities burn calories or you can also try Yoga
to increase metabolism
.Yes you can also do skiping rope but start slowly and gradully increase . Pay attention to your diet also reduce high carbohydrates diet and Fats to be reduced .By this you should come to shape again but take care of your health .Good luck.