hmmm... need people's input?

Soo I had sex last Saturday and I'm usually not the type that's like omg I had sex a week ago and I think I'm pregnant because I hate when people do that, but I feel really weird and I have the last couple days like tired, sick, twitches in my stomach, back pain, really weird stomach pains, diarrhea, nauseous, and my nipples are itchy. Maybe I'm just out of my mind lol but has anyone thought they were pregnant like I week in and ended up being right??