My boyfriend is lying about smoking and it hurts so much

Okay so me and my boyfriend have been together for 11 months almost a year now. he started smoking before i met him but i never knew about it then, and then he became a heavy smoker but told me he wasn't addicted, and i told him i didn't like him smoking because i was afraid of his health, and he told me he quit and i truly believe he had for about 10 months. until now, i have found cigarette buds around the flat , the smell of smoke on his clothes, and the occasional ash on the table. He admitted me me he has had the "odd fag" and that he dose not get addicted to them, but i cant understand how that can be, i thought cigarettes are are drug?? recently because he is stressed, but he never told me this until i confronted him about it. recently we were talking on skype and i swear i heard him light a cigarette and he claims he didnt, but i am almost certain it is what i heard. he finnaly admitted that he has been smoking occasionally but hiding it from me and his answer was that he dosnt know why he hides it, he got angry and told me to stop interrogating him. it really hurts me when he smokes. i tell my self that its okay its just the odd one, but what hurts most is that hes lyingg about it and hiding it! he wont listen to me with out getting angry about it. this has never happened before! i don't know how to handle this situation someone help?! :(