Thanks again everyone for all the advice. I'm going to try and schedule a professional bike fit in a week or so, which is the soonest I can get to a major city where they have a bike shop that actually does it.

The saddle I have now is just the one that came with the bike and although there is a small indentation in it, it is apparently not sufficient.

In the meantime I've been reading up about proper riding posture and been doing more yoga in the hopes to build more upper body and core strength to see if that helps me maintain a better sitting position for longer.