Duo combi test at 4 & 12 weeks with negative result after unprotected sex.stomach pains but no diarrhea,fever for almost 2months.need to test again?

HIV: Tests for p24 antigen and antibody to HIV.The overwhelming probability is that you are negative and will remain so. Nonetheless there are rare individuals who form antibodies late and so some recommend retesting at 6 mos. If you are having abdominal pain and fevers for 2 mos you definitely need to be seen by a doctor and fully evaluated, but doubt that this is in any way related to HIV disease.

Yes: It is recommended to get tested immediately and at 6,12 and 24weeks after potential exposure. On rare occasions have there been seroconversion that took up to a year. For the future always remember to use protection(condoms). At this time make sure you are not pregnant and get checked out for other causes of abdominal pain which may or may not be related to the sexual activity. All the best.