I've been taking the wrong folic acid!

Ca
My midwife only just told me I should be taking 5mg and I have been taking 4mg all this time. I am now 8 weeks 3 days pregnant! I am really upset that I was not told sooner! I have a BMI of 35 and am worried that I may have inadvertently harmed my baby ?. Why did neither my doctor, the midwife or the pharmacist not tell me earlier? They have all seen me!
Is anyone else in the same position?