If you are really in tune with your body, you can sense it the day after it happens. The first symptom most women have is a sensation of fullness & tenderness in the breasts. You also could be nauseous, yet crave foods that make no sense if you had a stomach virus (like Doritos or an ice cream sundae). To have a truly accurate result from a pregnancy test, you need to wait until after you've missed a period.
By the way, are you the one who might be pregnant? If so, do you know who the father is? I looked back at your previous questions, & it looks like you recently had a 16 year old boyfriend your dad didn't like, heartbreak over a breakup, problems with a stepdad, then a 20 year old boyfriend that your parents DO like. If you are indeed pregnant, PLEASE get some counseling. You might benefit from it even if you're not pregnant.
The symptoms are morning throw up, sore and inflamed ankles, increase in eating and the craving you have, belly getting bigger ( of course ) and your boobs begin to produce milk which makes them bigger