Day 3 monitoring & cancelled medicated cycle

I went in for day 3 U/S monitoring and I had a 13mm follicle and a 18 mm. They said it could be a cyst or a developing follicle. My labs were checked and my estrogen was Increased so they said no letrozole for this cycle and I could be ovulating soon. They said to go ahead & try on my own and no medication was needed. I’m s confused. Is it even possible to get pregnant early on in the cycle? Has anyone had a cancelled medicated cycle like this?