there are many symptoms of malaria: afternoon fever, sweating, loose of appetite, body malaise, etc.
If you have been abroad to a country where there is malaria, even if you took the medication religiously and completed the course upon returning home, but have become ill anytime up to ten weeks after returning and have intermittent fevers, which are the single most typical symptom of malaria. then go to your doctor and start treatment. A simple blood-test can determine if it is malaria but your should begin treatment as early as possible and then stop it if it is not malaria.