Sickness

My daughter had a fever 3 weeks ago, stuffed up, and runny nose. She now has a low grade fever again and still hasn't quite kicked the stuffy nose. Her nose isn't running anymore and she can breathe better through it, but I can still tell it's a little congested. She's acting totally normal besides a slight fever. I wonder if she could still be fighting the same infection? Has anyone ever experienced this before? If she doesn't get better in a couple days I plan to take her for a wellness check.