I am pregnant from 3 weeks.but sometimes i feel little bit pain in my utras. is that normal or something serious?

This is normal: You are very early in pregnancy. It is not unusual to have a small amount of cramping and even spotting. I always caution patients, though, in early pregnancy if you are having symptoms like pain or bleeding, you need to discuss them with your ob/gyn. They might be the earliest signs of an uncommon problem called an ectopic pregnancy.

Pregnancy: I am not sure what "utras" is but it possible to feel mild cramping from time to time.