Те сакам is term when you express love to someone and Те љубам is term using when someone allready is your beloved and also express love. I hope is corect

те љубам is more archaic and poetic form. It was more used in the past, like 40-50 years ago, the young people nowdays don't use it at all or vary rarely.

It's same, but we use "te sakam".

isto e