Help! Do I need a gastroenterologist?

I'm 24, back home after 2 years of living in Mexico. I've had abdominal discomfort, nausea and a sensation of fullness in my bladder for about 6 months now. Long story short - an infectious disease specialist found no parasites or anything abnormal in my stool/blood samples. I have already taken a course of the antibiotics for Giardia and so he has given me Donnatal for the symptoms but I am debating even taking it as the side effects seem like they could really worsen symptoms I already have: extreme fatigue, weakness, stress/mild depression. He told me that my only other option was to see an a gastroenterologist for something more invasive. Does anyone recommend the Donnatal? Do I need a gastroenterologist? Please HELP!

[tristan2]

Also, I should mention that I've had this anal itching/pain throughout these 6 months. Again, no blood or diahrea or anything, all internal problems.

[Kaneda2112]

From drugs.com:

"Donnatal produces many effects in the body, including reduced muscle spasms in the digestive or urinary tract, and reduced fluid secretions from certain glands or organs. The combination of belladonna alkaloids and phenobarbital is used to treat irritable bowel syndrome and ulcers in the intestine."

Apparently it can be habit forming. If you see a gi doc, they may want to have a look into your bladder or colon if you're still having issues. Not sure if there are any other options.