What Causes Tiredness And Vomiting Sensation?

i need to know whats wrong with me,i am 25 yrs old and my hieght is 5'2.. first i feel so tired and weak and i always vomiting and not throwing up any and i got an eyebugs, i thought i am pregnant coz i already felt this feeling before when i was pregnant to my 6 yrs old child now...i cannot remember when was my period and i had sex on oct 10.. im confused coz i already tried now the pregnancy test but the result is negative... whats wrong with me?pls answer me doc..thanks..