My 14 Year Old Daughter Is Complaining Of Constant Loud

My 14 year old daughter is complaining of constant loud stomach grumbling and just not feeling well. I'm not sure if it could be something like a parasite or based on her moderate level of anxiety she has always had and now in HS being intensified. I've tried giving her probiotics and digestive enzymes but doesn't seem to help much. I know the parasite testing in typical labs are not always accurate. I had a protozoa parasite from a caribbean trip I took about 7 years ago. Only a specialized lab in Arizona picked it up. I'm wondering what she can take OTC right now to rule anything out before going to a specialist (especially since I don't know which one.). Please advise. Thanks.