Have you been tested for a Methylenetetrahydrofolate reductase polymorphism?
It's also called MTHFR for short. If you have this, you may not be able to use folate from your diet. A folate deficiency can lead to a riboflavin deficiency - which exactly characterizes your symptoms. Riboflavin is required to make the enzyme "methylenetetrahydrofolate reductase" which is needed to convert folate to it's usable form. But some people don't make this enzyme properly and end up with a folate deficiency. Their bodies keep trying and trying, using up all the riboflavin to make an enzyme that doesn't work.
Supplementing with riboflavin is probably helping, but the real problem might be you need to take methylfolate, which is already in the converted form and useable by your body.
There is a genetic test for this, you can even order it yourself and do it from home. But with your history and symptoms your doctor should order it for you.
If you decide to skip the testing and take methylfolate, go slow and build up. Generally people with a deficiency experience side effects because the body has made a lot of adaptations to compensate, and it will need time to adjust. Also, folate will lower your blood sugar. So it's a good idea to have juice about 15 minutes after you take it.
If this is your problem, you have to take methylfolate supplements for the rest of your life. But, this polymorphism is cool because it's possible you have more resistance to malaria than people without it.