Doctor signing off on 8 weeks

Hi ladies,
Has anyone had their doctor sign off on 8 weeks off after birth for a vaginal delivery? I know 6 weeks is standard. I am asking for FMLA.
I am aware that I can take up to 12 weeks, however with how my job works, I have to pay for my own insurance ($1200/month) if I take more than what my doctor signs off on. So basically I plan to return to work after 6 or 8 because at that point it'd be very expensive to stay home. 
The secretary at my doctors office mentioned I could still try for 8 even with a vaginal delivery, but I don't know if she knows what she's talking about.