Thanks for your query.Based on the facts that you have posted it appears that you have pain in Rt side of upper abdomen since last 20 days and have been investigated.
scanning of the abdomen revealed Mild Enlargement of prostate In absence of any voiding symptoms it has no significance at all and should be taken as a ageing process .It should be monitored frequently by doing Ultrasound scanning and digital rectal examination
by a qualified Urologist
As regards gastritis that you have since last 15 years your pain in present context could be due to gastritis .
Please consult qualified Gastroentrologist for evaluation and take H2 receptor antagonist like Omeprazole
As regards taking VSL#3 that you are taking continue taking it ,It is a probiotic medical food that strengthens intestinal bacterial flora in the gut ant protects it from getting infection.