Multimillionaire “Bachelor” host CHRIS HARRISON is reeling from an expensive lesson he learned during his di­vorce from wife Gwen – never marry without a pre-nup.

“When Chris met Gwen, he hadn’t made his fortune, so he didn’t have a prenup,” explained a friend. “Now everyone is telling him that if he ever gets married again, he’d better protect his assets.”

Harrison is reportedly worth more than $15 mil­lion and earns $2.3 million a year, but he’s paying his ex a whopping $28,000 a month in spousal and child support, according to documents ob­tained exclusively by The ENQUIRER.

The 41-year-old performer and Gwen separated almost two years ago amid rumors that his wandering eye on the set of the ABC hit caused the collapse of his 19-year marriage.

As The ENQUIRER re­ported, allegations that Chris cheated on his wife erupted when Season 14 con­testant Rozlyn Papa – who was booted off midseason for having an “inappropriate” relationship with one of the show’s producers – hinted that Chris was doing the same thing.

 “Although he denied her allegations, his marriage exploded. But Chris wanted to keep the divorce as friendly as possible, and neither he nor Gwen hired attorneys,” said the friend. “He pretty much agreed to everything she wanted.”

In addition to receiving the hefty support payments, Gwen got about half of the couple’s assets. They also agreed to share custody of their son Joshua, 12, and daughter Taylor, 10.

With his marriage shattered, Chris has most recently been linked to Season 17 contestant Selma Alameri and says: “I will hopefully fall in love again.”