I am sorry to hear and hope that Teeka is alright.
As far as stomach ulcers - they can be difficult to rule in or out. They don't show on radiographs. Endoscopy is the best method to definitively identify them. Often medication to treat the ulcers if given if it is suspected. Ulceration can be a secondary problem with many toxins as well. Medications like pepcid, sucralfate, etc... are often employed.
If there is a toxin, then the kidney and liver enzymes will likely be closely looked at. Looking for pancreatitis (inflammation of the pancreas) could also be helpful. Also possibly abdominal ultrasound...
Fluid diuresis can be very helpful in flushing out toxins.
I wish Teeka a speedy recovery.