How to realise "anatta" of "Nama-rupa"

By noticing my abdomen while breathing , I can feel up and down movement of it . Also I can keep a mental notes as "up" and "down". When it is up there is "rupa of up" and "Nama of up mental note " and vice versa for down. But when it is down both "up rupa and Nama " already gone . So I have a glimpse of " anicca" . I do not feel directly "dukka" relate to abdomen movement but by applying same "anicca" for other temporary things in life I can get an understanding about "dukka" too . But I do not still have any clue about "anatta" , how can I understand the "anatta" using above scenario?