Hi CC! thats great u guys are TTC again soon!
I would either take your temp first thing when Ally wakes up, i havent heard of not being able to take it before 5am?
Another suggestion ive heard people doing is setting an alarm at a certain time each night, they then take their temp write it down and go back to sleep. If your the sort of person that could fall straight back to sleep and DH wouldnt wake up from the alarm it could be an option?
I think too a combo of CM and temp taking will help collate all the info to help you predict O time.
GOOD LUCK!!