Relationship Rehab

Now this is painful -- TMZ has learned, "Relationship Rehab" producers approached Heidi Montag and Spencer Pratt to work out their issues on the show ... and the couple flat-out rejected their offer.

Speidi's reasoning -- they're actually on great terms ... and don't have any issues to work out.

Sources close to Speidi tell us, the couple was initially intrigued -- thinking the show was actually about working out together ... as in yoga, or something like it. They had no idea it was for couples with real issues.

Linda Hogan's 23-year-old fiance just couldn't tame the cougar -- because he and the Hulk's 52-year-old ex-wife will be working out their issues on VH1's "Relationship Rehab" ... TMZ has learned.

Sources close to production tell us, Linda and literal boyfriend Charlie Hill have agreed to appear on the upcoming reality show, hoping to fix their crumbling relationship -- and taping is already underway.

Linda and Hulk Hogan got divorced back in 2009 -- and Charlie, who Linda had been dating since 2008, proposed a year later.

DMX will be working on his issues … the marital kind … on VH1’s upcoming “Relationship Rehab” … TMZ has learned.

The troubled rapper and his estranged wife Tashera Simmons have agreed to appear on the upcoming reality show in the hopes of getting their failed marriage back on track, a source close to production tells us.

The Simmons separated in July 2010 after 20 years and four kids together … yet they are still best friends, insists the source – and that’s why they want to give it another shot.

We’re told DMX feels Tashera is “one of the only people [he] truly ever loved and has been down with him through thick and thin.”

The thin? DMX cheated on his wife left and right – and even fathered six children during his extra-marital conquests.