Ive gone off food! Why dont i like it any more?

Recently ive really not enjoyed eating, its now got to the point where the only thing i enjoy eating is breakfast cereal so thats all i eat! Its not just that i dont fancy eating properly its that when i think of it or even cook it i really cant face eating anything to the point of feeling quite ill! Im not ill in any way, im not pregnant cos im a bloke so thats not it, i still feel otherwise healthy and ive just recently given up smoking so i would have thought i would be eating more not less! Does anyone else have any strange eating habits? should i worry about this as im not getting the right vitamins etc? im not sure what to do please comment. Thanks.