Firstly its great that you have lost so many cms, thats fab!
Secondly, if your clothes fit better, that is definately something you should go by, rather than kgs lost, as you may be building muscle (and muscle weighs more than fat) thridly If you have lost 30cms all over, it may be something like this-
3cms off neck
2cm off left leg
1 cm off right leg
4cm off left arm
3cm off right arm
6cm off waist etc etc..so little bits all adding up to 30cms if u know what I mean? You are doing well though either way, keep at it