Dean McDermott may have cheated on wife Tori Spelling because he wants an out of a "sexless marriage."

According to Star Magazine, McDermott has wanted to divorce Spelling for "some time," but the former 90210 star won't let him leave her.

"Dean wants a divorce and has for some time, but Tori is holding on for the sake of her business and her public image," an insider close to the couple told Star. "Her heart is breaking, and she is at a loss for what to do.

The big reason McDermott wants to leave Spelling is allegedly due to his sexual appetite.  Spelling reportedly tells her friends she's working hard to keep her marriage from falling apart, but their relationship has gotten so bad her husband refuses to have sex with her.

"Tori tells her friends that Dean is a sex maniac and constantly wants to have sex with her," a source told the gossip magazine. "But Dean, who does love sex, has shared with a friend that he doesn't want to have sex with Tori. They have not been intimate for more than a year and that alone has torn her up completely."

A divorce could also cost Spelling a lot of money, which could be another reason why she is holding onto McDermott so tightly, according to Radar Online.  The couple married in 2006 without signing a prenuptial agreement.  Spelling is reportedly regretting not having McDermott sign one.

"Dean offered to sign one, but Tori refused," an insider told Radar. "She truly believed Dean was her soul mate and there was zero need for a prenup."

"With the recent allegations that Dean cheated on Tori, she's now kicking herself for not securing the prenup with Dean," the insider added. "She doesn't plan on divorcing Dean, but feels that a prenup might could have prevented him from cheating on her."