The best thing to do, is make a point that your problem is becoming unbearable, it has been around for 3-4 weeks and not getting better. Don't go into specifics.
Then, ask to be refereed to a GI specialist, and they will push you up the priority list.
Keep it basic, like saying it started once you ate something bad, got sick, and it isn't going away.
They will start to consider gastro\intestinal parasite on their own, and order tests.
It seems to be the only way. If you make suggestions, they become resistant. Shroom