Rob Kardashian is hellbent on making a comeback following his breakup with Blac Chyna

Rob Kardashian is hellbent on making a comeback following his breakup with Blac Chyna and what's motivating him this time is another gal ... his daughter, Dream.

Recall Rob started to get back in shape and healthy again when he began dating Chyna, but it all went to hell when their breakup drama ignited. Rob spiraled back into another deep depression and gained back the weight he lost... and then some.

But now, sources are saying he's determined to lose it and has already hired a nutritionist and started working out again. His goal is to get back to the "old Rob" and he's determined to do it on his own ... with no help from friends or family.

But his friends and family are skeptical he can rebound without their help, but they do believe he loves Dream so much he might have a fighting chance.