People seem shocked when I say id like to be 12 half stone but thats what I was pre kids when I was 18yrs old...and I was slim and happy with my weight... But with me its coz people are used to me being 20stone plus so they think ill be too thin at 12 stone, Im gonna take it day by day I have no idea what my post 3 kids adult bosy will look like as I get lighter so I guess ill have to wait and see... technically 12 and half stone for my height is still classed as overweight Naughty BMI chart..
I dont think you have to worry to much about that as you look great in your pic.
I think rather then the BMI You have to go by what weight you feel is right for you and you feel good at.