I'm not really a bass player, but I would say you should try to stop memorizing songs, and just feel them. Its not always easy, but it you have to do it sooner or later.
I guess you could use a capo, but you would only be cheating your growth as a musician. I suggest You get very familiar with the location of the notes on the neck. if you use a capo, the notes will be in different places, and thats not good for your progress.