It sounds like you are not getting good sleep. Do you snore ? What kind of dreams do you have ?

Fatigue and headaches often mean a sleep issue. Being asleep does not mean you are getting good sleep. When my sleep apnea is a problem, it does not matter how much I sleep. I still feel miserable, with headaches, fatigue and cognitive struggles.

When you say the vitamin dose, what are you specifically taking and in what quantity ? What time of day ? With meals or empty stomach ?

There are some versions of some supplements that people react to in their stomachs. I think some react to fish oil. You could try stopping the fish oil for a few days to see it it makes a difference.

You may benefit from krill oil. It is highly concentrated so little is needed and stomach upset is usually much less or not at all.