I've been feeling strange can someone tell me what might be wrong with me?

about a week ago i went to the store and suddenly i got week, clammy and felt like i was going to faint. Since then i've been feeling weak, don't have much appetite, i have diarrhea, and a low fever (37.1-37.4) i am also in my 4th day of my period. the worse thing is that i feel scared when i have to go outside because i feel like i will faint again (is it in my head?) could it be just a stomach flu?