What Causes Nausea, Missed Period And Vomiting?

i have developed a couple of symptoms recently .. i have continous nausea and vomiting sensation for the last two weeks,but i vomitted only four or five times .. i cannot eat anything (although i have increased apetite) because of this (and do no thave any taste for any food) .. i missed my periods also this month .. i am feeling very week .. could you please advise wht are these symptoms refering to