Anybody having stomach problems on folic acid?

I have stopped taking my pregnacare as it was causing me severe diarrhoea and sickness. Since stopping I was almost instantly better. Now the only problem is I don’t exactly know what ingredient was causing me to be so poorly, so I want to start taking folic acid tablets instead but I’m terrified incase I get sick again, because it was horrible and because I can’t take more time off work. So I just want to know if anyone is solely on folic acid & vitamin d tablets and how they are getting on? Xx