Hello! During the session (4gr SR x 3gr ACRB) i felt terrible headaches - they was like series of waves going from the environment, entering the body, gathering into single point in the center of the head and tidal fall backwards cause terrible shock and pain. I was praying for this to stop.

Maybe it is browache because of serotonin syndrome? What can i do to not allow this happen again?

If you were fasting then that could be the cause of the headaches also dehydration can cause them. Also 4 grams of rue seems like overkill.

1) i eat two apples for 24hrs before session
2) drink not much water (about 500-700ml)
3) about 4gr, it's something i meet on other sites, next time i will try 3 and more acacia

Definately the fasting and lack of water then. Ive noticed I only get headaches when I fast when drinking aya, seems inescapable as I never get headaches normally.