Help Me! I need some advice/wisdom from mommies or mommies to be

I am 3 days into my "fertile window" and I had unprotected sex with he BF 2 days before my "fertile window" was supposed to start. What is the likely hood that I am pregnant? Also how long would it before I could concieve? I've never really been in tune with my ovulation schedule but now that I feel that it's a real possibility that I could be pregnant I've read up on it a little. So far I have been tired a lot, I have been having a headache almost every day, and I've been exceptionally gassy(sorry for tmi). I know it's been a long read but please any advice you ladies could give me would be great!