Suggestions for the driving hazzle with an office bag

Hello guys ,

So ive gotten a new bike two weeks ago and have been commuting with it for my work and beyond. I'm facing a lot of shoulder and neck pain due to the bag constantly pulling my body behind. I carry laptops,some file,a rain coat and a few books for my work and its a wild Craft bag.

This is my first bike and previously , i've only driven different kinds of scooters.

So i want to ask my fellow bikers, what do you do for this issue? I feel sever lack of storage/comfort space (In the trunk or below near the foot rest was amazing space to carry my bag on my scooter).

help a fellow bikerMan out . Thanks