Thanks for that info and choosing the Apple Support Communities. Based on what you stated, it seems you are having issues with your battery on your iPhone SE since updating the iOS software. If you haven't already, please restart your iPhone as iOS clears cached data and does other system optimizations when you turn your device off and on. Then go to Settings > Battery > Battery Health and check the recommendations shown there.
Restart your iPhone, iPad, or iPod touch
iPhone Battery and Performance
Be sure to check out the section titled "How to maximize battery performance" for additional steps you can take to maximize performance.