I remember having the same feelings whan Mason was about 4 months old.
Looking back now I guess the reason I waited untill he was almost 1 to try again is unclear. It was like I wanted to but something always made me stop IYKWIM. DH was a bit against having another one so soon, as he was concerned about my ability to manage two so young. I wasn't thinking about it in that way.
We decided to try again after my period returned when Mason was 11 months. Looking back I think it was the right time as I had a lot of enjoyment of Mason as a baby, and as a small toddler too. He was 21 months when Angus was born.
This time I waited a bit longer though