I have a similar situation, but I don't have to carry my laptop ALL the time. When I have to carry the laptop or other heavy stuff I throw it in a panier.
But when I'm just carrying clothes and the usual day-to-day stuff I use this most excellent backpack:
Commuter Backpack
It is truly excellent for commuting on a bike. I used paniers exclusively for years, but I MUCH prefer this backpack. It may be a coincidence, but I have way less broken spokes using a backpack.