Why am I losing weight?

I am 18 and i used to weigh 7 and a half stone, i have not changed my diet, if anything i eat more junk food like mcdonalds and pizza's etc i haven't started exercising more, i don't throw up, i eat whenever im hungry which is most of the time but somehow i have lost over half a stone, whats wrong?Why am I losing weight?
i have a feeling you might gain weight though like after sometime you might see you gained weight suddenly, OR your weight machines disturbing or wrong, it happened to me once. anwayz eat healthy goodluck!!
you need to go to the doctor and have some blood work/labs done to make sure there isn't a medical reason for your weight loss. there are many causes that should be ruled out.
Go to the doctor
Maybe you caught tapeworm? see a doc..
maybe you're depressed.. .depression is known to cause weight loss cuz more often than not , depressed ppl tend to have reduced appetite so they eventually lose weight.but in your case , you said you're eating more if anything.that's wierd.you really ought to go consult a doc about this.it might be something serious.just don't take it lightly.
and if you figure out why you've lost all that weight , please leave an email.i would really like to try that out just like you did and lose a few pounds.haha.