Thank you for asking your query at DoctorSpring.
HIV Ag/Ab combination test is a reliable test without much false negative results. So basically its reliable and you consider yourself to be HIV negative. The test also looks for p24 antigen, which will occur early in the blood. (Usual tests only look for Antibodies)
The symptoms are probably unrelated. Early HIV is asymptomatic in most cases. The symptoms you are having is not typical of HIV sero conversion illness either. You will only need symptomatic treatment. You can take an OTC pain reliever like Ibuprofen for the aches. Diarrhea should resolve by itsown in 2-3 days. Drink planet of water, avoid milk and spicy food meanwhile.
Just to be sure (for your mental peace) you can do a repeat HIV antibody test after 5-6 weeks. I am sure this will also give a negative test and you can also be sure for the record
Hope this helps
Please feel free to ask followup questions.