Hi, from what I remember my family doctor advising me.. Evening primrose oil is recommended to help with pms symptoms, but not recommended for pregnancy. So if you use it while TTC, it shd be stopped when u suspect u are pregnant. A quick read at WebMD website also indicates in its 'side effects' section that it is possibly unsafe for pregnancy. It is more likely to be recommended at a later stage of pregnancy, near birth, to help with labour.
Women who are not pregnant only need 400mcg of folic acid a day, and this is usually found in regular multivitamins. So until 3 months before I TTC, I just plan to continue with regular vits as per my doctor's advice, as it gives me the recommended amt of vitamin b too.
Have you seen a doctor for a prenatal visit?