abdominal pain while pregnant

hi, im currently 19 weeks pregnant and have had abdominal pain with headache and dirrahea, i have been drinking plenty but it wont go away it seems that every thing i eat just goes straight threw me. i have triedn dry biscuts but nothing works. i have had ovarian cyst before. im pale in the face than usual and i feel drained like im tired. even though i have been sleeping well at night time. does any one now what i should do. thanks!!