What Causes Weight Loss, Lack Of Appetite, Itchy Breasts And Headaches?

For the past weeks i haven't been feeling like myself lately. I have had my period and took a test and it came out negative but i have been lossing weight, lack of eating,I sleep more often,Im always feeling jittery/nervious throughout the day,i have itchy breast,serve headaches,i sometimes crave certain foods,and my boyfriend has put on a few pounds and is also eatting a lot more!! What does this actually mean?