Weight fluctuation

this is more just a rant then anything
is it just me or does anyone else have weight that tends to go up and down.this keeps happening to me and ive no idea what i am doing wrong,i am not eating more then normal or exercising less,i weigh myself same time everyday,one day i might be 9st the next 9st 1 then next day 9st again,it never goes any lower then that,just goes back and to between them both.i know their are some anorexics that dont eat at all but i cant just stop eating.wish i could to be honest but i am so weak willed.its like my body refuses to go any lower then 9st.at 9st i am not under weight,i found out for my height 5ft 8 i can go as low as 8st 10.its so frustrating