I had unprotected sex over a week ago and had bleeding after that lasted 5 days. now one of my nipples has begun to change color. could i be pregnant?

Hard to guess: It can be hard to guess whether a woman is pregnant or not. 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, or after having a "weird" 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.