If new calendar events entered on your iPad do not appear on icloud.com, go to Settings>Mail,Contacts,Calendars>Default Calendar on your iPad and be sure you have selected an iCloud calendar as your default and not something else like On My iPhone, a Gmail or Yahoo 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 your settings are correct and new events still aren't appearing on icloud.com, add any missing calendar events from your iPad to your calendar on icloud.com. Once the calendar on icloud.com is up to date with your iPad, go to Settings>iCloud, turn Calendars to Off, choose Delete from My iPad when prompted (they will still be in iCloud), then after a 15 seconds or so, turn Calendars back to On. Then add a new event on your iPad and see if it appears on your calendar on icloud.com now, and on your other devices.