and less so
I don't like children, and less so, since I knew I couldn't have them.
You could just say
I don't like children, and less, since I knew I couldn't have them.
But it works better when the word "so" is included.
"..., and especially now that I've found out that I can't have them."
I was taught that "saber" in the preterit corresponds to "found out" or "learned" (a piece of news).
"No puedo" is in the present tense.