My 920 has not had this problem severely since early days of 8.1 preview, but I have had a couple mild issues that I've addressed in a couple of ways. BTW, my battery in moderate use typically lasts 17 to 24 hours between charges, although I routinely charge it every night while I'm sleeping. Obviously, I don't know how my 'moderate use' compares to what you do with your phone. The heating up, though, is a sign that you have a problem that I don't have, so maybe there's a way to fix it.
I assume you've checked the usage page in Battery Saver to be sure you don't have any runaway apps and that only apps that you want running in the background are enabled for it. That's the first step.
Second step is to try a normal shut down and restart of the phone. If that doesn't help, a soft reset or two (sounds like you've already gotten this far). If that doesn't help, run your battery down all the way, let the phone sit for a bit, then apply a full recharge. If that doesn't help, it's time to try a hard reset. Make sure you have a good backup, hard reset, and restore. I've never gone beyond this level, but if you're still having problems, you can try a hard reset without restoring and set your phone back up from scratch (I know, ugh!). Of course, the ultimate attempt is to use the Nokia Software Recovery Tool to go back to whatever Nokia considers the 'base' level for your phone now (might be Black/8.0, might be Cyan/8.1, depends on just where in the update process your phone falls at the moment), then decide how far you want to go in updating. Maybe you want to wait for MS to release another set of patches for GDR1 before loading it back on, if you have to take this severe action. It's all up to you.
Facebook
Twitter
Instagram