I have an iPhone 6, without Apple Care.
A few months ago I noticed it got unbelievably, incredibly hot during use, both on and off the charger. It would also use the battery quite fast, up to 2% a minute sometimes, and would often be completely depleted by midday from a full charge, after it being in my pocket at school with time and social media checks being the only use. It also was in mint condition, having lived in a Lifeproof case for its entire life.
However, I noticed the case started to bulge just underneath the left volume button on the side, pushing outwards slightly. Could this be a battery problem? Apple Support told me my battery health was fine (90%), so I should go to an Apple Store to get it looked at. As the closest store is 4 hours away, could anyone tell me if this is battery related or not?