Tori Spelling‘s weight has plunged to 91 pounds, sources say – and friends and family fear the pin-thin star faces a serious health crisis.

The former Beverly Hills 90210 actress is so skinny the bones in her back are sticking out – a sign that her calorie-starved body is using her fat and muscle stores for fuel, medical experts say.

But the 36-year-old mother of two wants to lose even more weight!

"Tori thinks she’ll look better thinner, and she won’t listen to anybody," divulged a family friend. "Those are classic symptoms of anorexia, but Tori denies she has an eating disorder. Yet sometimes she doesn’t eat much more during the day than the leftover bits of food from her children’s meals."

Tori, who is 5-foot-5, has been shedding weight ever since her daughter Stella was born last June. But friends say her weight loss has accelerated alarmingly in the past few months.

Her jean size has dropped to a size 00, and she’s gone from 95 pounds in April to a skeletal 91 pounds now, according to the family friend.

Hubby Dean McDermott,42, is worried about Tori’s weight loss, said the source.

"When Dean tried to mention his concern, Tori almost bit off his head and wouldn’t talk to him for days. It’s a real dilemma," said the family friend.

Tori’s rep, however, insists she’s “100 percent healthy” and weighs the same as she did before her pregnancy.