Uncertainty

I am still trying to decide when my next bike race will be.  I meet with a personal trainer weekly.  This week we are doing an assessment since we have had 12 sessions together.  Maybe after this evaluation, I'll know more about her opinion on when I should try again.  There is another metric century on July 20, but I'm afraid that might be too soon.  I feel like my back is about 90% back to what it was before the June attempt at the 62 miles.  I wonder if I might need to do a 31 miler before trying the bigger one again.  I hate not knowing what I should do!!!