Abby,
I have a rolling backpack and intend to use it even if I only have to carry supplies to one class - you know why? I purchased my books yesterday and they are huge! Add to the books a binder and/or notebook paper that you might want to carry - not to mention incidentals - and I would rather spare myself from hurting my back first and foremost, but another thing I would be afraid of is hurriedly trying to switch back and forth and accidentally showing up somewhere without something vital - like no calculator for a dosage calc test where they don't provide one for you - you know?
Just my

By the way, it's okay to be concerned about every last nit-picky thing!! I mean, me and my study partners are nit-picking all the way to what color binders/notebooks to buy that will match the color of our books that way everything will be organized

Don't worry - you are NOT alone!!
Traci