Am I pregnant please help

Okay so this week I had  unprotected  sex on Tuesday and it's my fertile window. I didn't realize it was! 
Now it's Friday and for the last two days I have been feeling sick with diahrea and haven't been able to eat much. I have stomach pain. Is it too soon for implantation or is that what is happening? Could I just be sick? Or am I pregnant? Please help 
Update: sharp pain in lower right abdomen growing worse