Fertile window?

Brittney • I`m 32 years old and have a almost 2 year old son (bday 9/3) and pregnant with our little girl (due 10/4)
When does everyone's fertile window start? Mine starts on the 11th...I think I'm going to BD 2 days on one day off. I will most likely O Friday or Saturday. We BD everyday last cycle...I was sore and maybe the hubs does not have the sperm count for that. LOL! This is my first cycle tracking BBT (started after O last cycle), waiting to see if my temp goes up!