Not trying but not preventing after successful fertility treatments?

So my son is a year and a half now and I had a tough c-section delivery with him and he went straight to the NICU for a pneumothorax in each lung. I have PCOS and we went through fertility treatments up to IUI with tons of injections to get pregnant. Before having my son my period was irregular and would disappear for months at a time. Since my period came back after my son I’ve been fairly regular every month within a few days of expected period.

Anyways on vacation this past week we had a little fun and didn’t pack protection. Afterwards this lead to a few conversations about where we stood on a second baby. We’ve come to the conclusion we are done with protection but aren’t ready for the emotional/mental/physical stress of full on trying.

I am in serious doubts we will get pregnant without intervention but I would like to know if anybody has been so lucky?