How does one know?

Okay well let me jus be honest and say I cheated on my bf..well I told him an now he wont leave me alone about sayin im Pregnant... Because the fact I felt sick today and stayed home...Im not feeling myself ...I am started to eat alot more then usual..I like crave Salads or like chinese food. I am startin to feel more sleepier...so wat is there a possibility or is this jus all in my head?