Create a test even on your iPhone calendar, then check your calendar on icloud.com from your computer to see if it appears there. If not, go to Settings>Mail,Contacts,Calendars>Default Calendar and be sure you have selected an iCloud calendar as your default and not something else like On My iPhone, a Google calendar, etc. If you haven't, make this change, then add a new event and see if it appears on your calendar on icloud.com now. If new events still aren't appearing on icloud.com, add any missing calendar events from your phone to your calendar on icloud.com. Once the calendar on icloud.com is up to date, go to Settings>iCloud, turn Calendars to Off, choose Delete from My iPhone when prompted (they will still be in iCloud), then after a minute or so, turn Calendars back to On. Then add a new event on your phone and see if it appears on your calendar on icloud.com now.
Then repeat this process on your iPad.