Doc says Gastritis but doesn't fit Alarming Symptoms

26 yr Female.  I have been experiencing reflux with small amounts of vomit, and constant gas.  Constipation and diarrhea, with dark blood and mucus in stool.  Pretty fatigued, and sleepy, oh and obviously upset stomach, painful mid and lower abdomen, for a good two-three months.
I went to visit my doctor, and think I made a mistake by doing so on Christmas Eve, because she very confidently declared gastritis and sent me on my way.  Well I barely had a chance to tell her the symptoms, all she did was push on my stomach.  I'm a nursing student, and read up on gastritis, my symptoms don't really fit with that diagnosis very well and I don't have anything to trigger it either.
I haven't eaten gluten for 18 months, cut out dairy three weeks ago, I don't drink alcohol ever, I don't go to restaurants or eat high fat foods.  I also don't like spicy or salty foods.
I had an emergency appendectomy 8 months ago, and up until 10 weeks ago seemed to be doing fine.
My doctor put me on omeprazole and said I'll be fine in two months, but it's not helping so far and the symptoms scare me.  I asked her if an endoscopy was an option, and she said that a gastroenterologist would want me to wait two months to take the omeprazole anyway.  
Any similar experiences?????

[Ratnakar Kini, MD]

Hi,
As you said all the symptoms you have mentioned do not fit in to gastritis.
Altered bowel movements with blood and mucus in stool and abdominal pain need to be evaluated with colonoscopy.
The fatigue and 'sleepiness' you have could be due to anemia due to blood loss.
Consult a gastroenterologist and have colonoscopy done.