is this loose skin? can I do something about it without surgery ? :'((

I've improved my shape a reasonable amount by eating at maintenance and doing home YouTube workouts - try Caroline girvan epic heat series of 50 half hour sessions. Use heavier weights. 2-4kg isn't really going to build muscle. You need to work hard! And you will get good results if you put the effort in at age 28! I'm 56 and have noticed changes for the better.