What Tests Should Be Done For Pale Colored Stool With Abdominal Pain?

.my daughter is 3.5 yrs old. about 15 days earlier she started complaining that she is tired again and again. and off and on i have been noticing that she is passing pale coloured stools. she also complains of abdominal pain off and on but mostly when i insist and force her to drink milk or eat something. i remember noticing pale coloured stools of hers before too but i dont exactly remember the time or dont remember the how much time have gone by when i noticed it.i dont remember it exactly. why is it happeneing frequently. what tests(blood, ultrasound, urine tests etc) need to be done before i go to see the doc personally. thanks