Hi have had nausea, gut rot feeling, weight loss (30 lbs), tachycardia, dizziness. normal endoscopy/colonoscopy, scans... what coukd it be?

See an internist: The weight loss, if over a short period is concerning, if you've traveled recently this could be an intestinal parasite, but the dizziness and tachycardia could be something else when you put the symptoms all together. See a good internist, get a good physical exam, and probably a stool sample, urinalysis, and blood work to see what is causing you troubles, it may not be in your GI tract...Meds?