Thanks for reaching out cammi195,
It sounds like you're missing events in your calendar following an iOS update. We can help.
The first thing we'll want to try is to make sure all your calendars are accounted for and enabled. You can check out these steps to Set up multiple calendars on iPhone:
See multiple calendars at once
To view multiple calendars, tap Calendars at the bottom of the screen, then do any of the following:
* Select the calendars you want to view.
* Tap US Holidays to include national holidays with your events.
* Tap Birthdays to include birthdays from Contacts with your events.
Set a default calendar
You can set one of your calendars as the default calendar. When you add an event using Siri or other apps, it’s added to your default calendar.
1. Go to Settings
> Calendar > Default Calendar.
2. Select the calendar you want to use as your default calendar.
Turn on calendar event alerts
You can turn on event notifications for calendars you create or subscribe to.
1. Tap Calendars at the bottom of the screen.
2. Tap
next to a calendar.
3. Go to Event Alerts below Notifications to turn event alerts on or off.
4. Tap Done.
Hope that helps.
Take care.