Ok so even after i backed up my iphone, not all of my messages were retrieved back. why is this ? and only certain numbers came back not all.

What happened to your messages? Are you setting up a new phone? Or did you delete the messages? If you're using iCloud Syncing for Messages, your messages are not part of your back up. Once you delete them, they are gone.

Sometimes, but not always, if you start a new conversation with the person, the old messages will reload.

Hey babii_dream sorry your having problems with this but when you backed up your old phone you may not have had enough storage to back it all up