Do pregnant women have free prescriptions and dental care?

I was given prescription for Folic acid,the doctor said its free for every pregnant woman. In chemistry though they asked me to pay saying prescriptions are free only after 3 months of pregnancy.Information on internet says EVERY pregnant woman has free prescription and dental care.So how is it?I am in England.
Allright, if I have the certificate,can I get the money I paid back? The problem was that the chemist did not want any proof of pregnancy from me.She simply said the pregnancy is only two months and I have to pay(doesn’t matter if I have any exemption certificate). I still have the prescription paper as she sold me the same tablets over the counter as it was cheaper-though still expensive for me.Can I complain somewhere and get my money back?