How soon after ..?

Stephanie • Hi
How soon after having unprotected sex is the earliest you will start to feel pregnancy symptoms? 
I've been having cramps and back pain, along with sore breasts and major fatigue. I've also been getting headaches randomly and feeling dizzy and gassy (sorry if that's tmi) 
Anyways, I just feel like it's way too early to be feeling like this even if I am pregnant. Problem is, it's still too early to get a test as well. 
So just wondering when the earliest possible symptoms can appear ?