Hi and welcome to HCM.
I dont think your abdominal pain
is related to STD. YOu have pretty nonspecific symptoms and it is hard to give right diagnosis. Is this pain associated with meal or not? If yes, then gastritis or biliary colicae are first you should think of. If you have diarrea or constipation
then it can be IBD. if you have blood in your stool then various anorectal disorders should be considered. If you have fever or pain while touching your abdomen than you should go to Er to rule out something serious. I suggest you to start with basic lab,abdominal ultrasound
to check gallbladder
. After that some more unpleastant tests such as gastroscopy and colonoscopy
should be done.
Wish you good health. Hope I ve answerd your question.