That’s why I’m on Lexapro now for my anticipatory anxiety in social and normally stressful situations. Anxiety really exacerbates my blocks. I take Propanolol as needed 1hr before heavy speaking situations to eliminate any of the physiological effects of adrenaline and stress. Makes a massive difference! If you want to go down the vitamin route, you could get onto Magnesium Glycinate (or Magnesium L-Threonate), L-Theanine and Vitamin B1.