Can I ask...

I moved farther from my office to stay closer to my son's new school. It is the second week since we moved. 

I have started running home from the office at least three days a week to better use my time. It is a hilly challenging 12KM route.

Is it ok to run with a 3-5 pounds backpack? I feel harder but dont feel particularly difficult or discomfort.  

Thanks.