9.3.1 update problems

Hi

Since installing the 9.3.1 update I have been havng real problems with my iphone 6s

To start with the battery life often only lasts for half the day where as is used to last more than a day. Then it started crashing requiring a 2 button reboot. Initially this would happen just occasionally sometimes when it rang. Then last Friday I was taking photos. It work at first but the it started to crash constantly needing a 2 button reboot every time. This happened at least 10 times before I just gave up trying to take photos.

In addition the phone often feel hot.

I always close down apps completely so don't have lots of things running in the background......Anyone have any ideas what I can do? I can't take it into an apple shop because I live on an island and won't be on the mainland for at least a couple of months

Thanks in advance