If i have sex unprotected and he came in me what chance do i have of getting pregnant ?

That's how it works: Getting sperm inside one's vagina is how babies start. A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test.