I've experiencing pregnancy symptoms for almost 3 weeks now. i feel cramps on lower side of my abdomen, both left and right. also i feel lower back pain. but last week i have my period that lasted for 4 days. am i pregnant?

Maybe not, but...: If a woman has her normal regular menstrual period, then she is presumed not pregnant. If she thinks she is pregnant, then doing a urine pregnancy test the week after missing her "normal" period, the week after getting a "strange or abnormal period," or 3 weeks after having sex, should give an accurate result. Pregnancy tests are inexpensive and sold everywhere.