I dont think my bf is attracted to me and he wouldnt tell me if he wasnt so how can i tell?

ive lost like 10 kgs since ive been going out with this guy. i guess i make more of an effort now and exercise because i want to look good but i dont think he likes me being thin! he would never actually tell me that but hes constantly saying that i should eat more and giving me the :/ looks about it. i always subtly try and say something like 'does dress make me look fat?' to see what his reaction is but he just says im y. i have a strong feeling he isnt attracted to me because ive lost weight... why wont he just tell me?