Tamica and Marcus

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Dr. Berman says Tamica created a fantasy based on the hardship of her childhood. "It was a lot about money, and they are—and were—very comfortable by most standards. But it didn't feel like enough," Dr. Berman says. "She was so scared about that piece of it and was putting that responsibility completely on Marcus. And when he didn't live up to those gazillionaire expectations in her mind, she started seeing him as a failure."

As a result, Dr. Berman says Tamica began to resent Marcus. "She withdrew from the relationship, and if you're resentful toward someone, you're not going to want to have sex with them," Dr. Berman says.

Tamica admits that she withheld sex from Marcus as a punishment. "I felt like he wasn't worthy of me having sex with him if he could not do things I needed him to do," she says. "I would give it to him in rations."

Rationing sex, Dr. Berman says, is protecting yourself when you don't completely trust your partner. "When you have sex with someone, you're giving them a gift," Dr. Berman says. "You're sharing something very sacred and powerful with them, and if you're not feeling good about them and good about the relationship, it's really hard to do."