Membrane sweep

My midwife told me at 38 weeks she would sweep my membrane. I want to go into labor naturally like I did with my last baby so plan to have her do it but the problem is my next appointment I am 37+5 and she said I have to be 38 weeks. My appointment after that I’ll be 38+6… I am frustrated she can’t just do the sweep at 37+5. I’m pretty much 38 weeks. Should I just cancel appointment and make it later that week so I’ll be 38 weeks exactly?