Hi! So excited for you! This is normal for my first ivf they started me on day 5 and actually stopped stims from time to time when my fsh got too high which it did twice. I did a consult w dr c-0hen and she told me that generally if fsh is under 10 on its own they will start on day 3 or 4. If it's higher than 10 they like to wait. In fact for my 2nd ivf my fsh was 9.5 and I started on day 4.
Good luck!! I hope this is the one! I look forward to hearing updates:)