The strange part is that you get headaches when you DON'T use the tinctures, or don't use enough. That's puzzling. I've never heard of people getting headaches from not using it.
Do you have a health professional you could talk to about it? That would be best.
I think you may be taking a stronger dose than needed, but I'm no doctor. Perhaps you could gradually reduce your doseage a little at a time, or try a less powerful strain.

EDIT: Yes, there are many strains of indica, sativa and hybrids of both. They all have different ratios of active ingredients and varying effects and potencies.