Nas the effect was immediate.
The key is probably in the dosage, and the timing.
You are also missing B6. Based on previous posts by others, B6 is very important.
Why waste your time trying out this and that. What I did was buy all of them together (Vitamin C, E, B1, B3, B6, B12, D, Fish Oil, Lecithin, Magnesium, Zinc and Curcumin) and take all of them together about 1 hour and 20 minutes prior to orgasm. It knocked out pretty much all my symptoms, don't ask me which actual vitamin was responsible, I am too scared to eliminate any of them to narrow it down because my POIS is so severe. So I just take them all. I even include Vitamin D now.
I do not take them every day. I believe it is key to only take them prior to orgasm. Not on other days. You don't want to build up an immunity to them.
The doses I take have been listed in a previous post. I do not take the B complex, the doses were really low compared to taking each one individually. I would take each B individually. For example in my B complex there is only 50 mcg of B12, but if you buy B12 individually, it is 1000 mcg. Literally 20 times the amount. In testing phase, I would not waste time on smaller doses, I can always reduce the dosage later...
Good luck!!