what job exactly do you want?
if you want to become a psychologist, then obviously psychology despite the workload [question - have you done psychology examinations before, like A level?]
if you are worried about the workload, maybe it is better to avoid medical subs completely as they are very very content heavy
and as offshore-cauldro said, an interior design degree might not be necessary to pursue a career in that field
i was also interested in that for some time, and there are many websites online where you can design rooms for free and courses [like coursera] that you can take
but if interior design is your chosen career then obviously having the degree will give you an advantage