How’d ‘Cosby’ kid get preggers?

“THE Cosby Show” star Keshia Knight Pull

iam’s marriage to NFL player Ed Hartwell fell apart after just two months, and he fears she went behind his back to get pregnant after they stopped having sex.

Speaking to the media for the first time since he sensationally filed divorce papers on Monday, days after Pulliam announced she is pregnant, Hartwell, 38, exclusively told “Page Six TV” that their marriage was torn apart by jealousy, disagreements about starting a family and suspicions about infidelity on both sides.

Hartwell, who married Pulliam, 37, on Jan. 1 after dating for four months, said things quickly soured and they stopped having sex — but she was so fix- ated on getting pregnant that he suspects she went behind his back to do it.

He says that in February, after realizing things were going off the rails, he “had a sit-down” with his wife, who played Rudy Huxtable on the oncebeloved NBC show. “I said, ‘I think we probably messed up. I think we moved too fast,’ ” he told us.

Hartwell says he confessed that his ex, whomhe dated for four years, had “lost a baby,” and it made him realize he still “cared about her.” Pulliam, who’s now four months pregnant, was so upset that she virtually disappeared from his life, he says. Hartwell said she fled to visit a spiritualist and “started going out with friends” and “sometimes not coming home at all.”

Following the confrontation, Hartwell — who has a 9-year-old son, Ed Jr., with his ex-wife, former “Real Housewives of Atlanta” star Lisa Wu— says Pulliam was desperate to have a baby by any means possible, through in vitro, adoption or naturally. But he had told her he didn’t want more kids, and “that’s one of the reasons we actually stopped having sex,” he said.

But Pulliam did become pregnant, and now the former Baltimore Ravens linebacker has asked for a paternity test. He says he can’t understand how it happened. “As time kept going past . . . some things just weren’t adding up,” he said. But Pulliam has insisted, “I have never been unfaithful to my husband. This is his daughter.”