Hi there!
Well, without a clinical evaluation it would be difficult to determine the cause of your symptoms. Possibilities that may need to be considered include infections, inflammation, malabsorption, motility issues, hormonal/ endocrine imbalances etc. I would suggest getting this evaluated by a primary care physician or a gastroenterologist for an accurate diagnosis and appropriate management.
Hope this is helpful.
Take care!
I should say actually it's closer than the size of a marble than a golf ball