breast pain

Hello! I'm a first time mom-to-be and currently 10weeks pregnant. I've read that there are may changes that will happen to my body,including my breasts. However, there are times when my breasts hurts, the other one hurts more than the other. Next time, it will be the other side that will be more painful. Though its bearable, but is this normal? I've checked my breasts for any lumps, fortunately there are none..