Dull Stomach Pain & Tenderness

I am male of 39
3 months back dull stomach pain started to me which was in the form of cramps in upper stomach with very mild nausea
I visited doctor & he advised some antibiotic taking it as infection & also advised me USG & Stool test for Ocult Blood
But condition did not improve & I changed the doctor
I get the report of USG (normal) & Stool test (Ocult Blood Positive)
Second Doctor taken it as GERD and advised antcid & other medicine
Further condition did not improve, so he advised for Gastroscopy

I consulted a Gastroentrologist, he given some medicines initially but later advised gastroscopy
I got the gstroscopy done & results found normal

Then doctor advised me medicine for IBS & Also adivsed me to repeat Stool Test for Ocult Blood
There was improvement in condition , but after 20 days my stomach again started getting mild cramps
I got my stool tested for Ocult Blood, & it was positive

Now doctor has again advised me antibiotics

After taking Antibiotics now
1. There is reduction in cramps drastically, but not fully gone
2. I feel tenderness in my stomach
3. Occassionally I feel mild Nausia

Otherwise there is no change in my apetite and weight

Can anybody have this type of problem & explain why??