Hello, I've Been Having Some Stomach Issues For A While
Some tests should be done.
Detailed Answer:
Hello and thank you for choosing "Ask a Doctor" service for your query,
Have seen your details and I appreciate your concerns.
Left side of middle and lower abdomen contains large intestine and pain in that part is suggestive of inflammation and spasms there.
As far as black color of stool is concerned usually blood is contained if stools are TARRY BLACK like charcoal in nature. However a test called stool for occult blood is done to find out if it's really blood or not.
Secondly a CT scan abdomen should be done to rule out diverticulitis.
Antibiotics could be a reason among many reasons causing diverticulitis. For e.g food habits,Alcohol,Smoking,Viral infection etc could cause depletion of good gut Flora causing bad bacterial colonies to flourish.
A CT abdomen should therefore be done.
I would suggest you to go for few test like
-Stool routine culture and microscopy
-Stool for occult blood.
-CT Abdomen/Ultrasound abdomen.
Stop taking Omeprazole. Its not necessary that every salt suits every person.
Instead of omeprazole take Ranatidine 150 mg once daily.
Eat very light home cooked vegetarian food.
Follow up with the test reports.
Trail and error(Guess work) policy is not a good idea.
Hope I was helpful,
Thanks!