Intense headache after taking Niacin

[Suppertime]

Initially taking Niacin, I would feel 80% normal. But after a few months, I stopped taking it completely.

Now that I've started masturbating again, and taking Niacin, I've been getting a headache the morning after all the way to night.

I even tried taking the smallest amount of dosage, cutting a pill into 10% of 100mg. Still the same... anyone getting similar headaches?