Not all people have sure signs of being pregnant--with my first pregnancy I never had any symptoms at all and didn't even feel pregnant until I actually started showing................
i know how you feel. i never get my periods. and have taken plenty of tests. i wouldnt worry about it. all your symptoms are the symptoms of being STRESSED!!! come on girl. you know your body better than anyone. a girl would know right away if they were pregnant or not, but yes, there is still sooo many worries. if you have gotten all negative tests the only thing to do to help you not worry is get an exam. from what you have written though, it seems like stress. so iwouldnt worry anymore :)
it could be a number of things... rom what you're saying, i'd suggest getting tested for pcos, look it up on google for symptoms. However, i'd hope this isn't the case.. but just a suggestion.