I can't really say . . .I had problems TTC my 2nd DD (no issues at all with #1), so I was almost 100% sure I couldn't get pregnant. I thought I'd need progesterone again.
This was only my 3rd cycle PP-- the first I didn't chart, the 2nd I did but didn't temp on "the" most important dates (to count my luteal phase) 'cause I was sure I wasn't ovulating . . .but I knew our timing was all wrong anyway . . .and then this cycle.
So, we didn't think we could conceive but were not TTA.
Far too much info than what you're asking!