If you tested using a duo combo ab/ag HIV test 28 days after finishing your PEP, and it was negative, your result was accurate. HIV is never diagnosed through symptoms, and as you are having malaria as well, you better look for a treatment now.
All the best.
After PEP completion, people are advised to be tested at 6 week, 3 month and in some countries 6 month-mark(after the completion date, bot exposure) . You're most likely negative, but test for conclusive results.