Is it ok to use the 5mg folic acid dosage instead of the normal suggest 4mg dosage when trying for a baby?

You can: there is no known toxicity with folic acid, although it is unlikely that more is going to help. The normal daily requirement for folate is less than 1 mg, and 4 mg is probably overkill as well. Prenatal vitamins generally contain 0.8 to 1 mg (800 to 1000 micrograms), so 4 mg is NOT a normal dosage. It can't hurt but will be unlikely to help more than the usual 1 mg amount.