'What's Happening!!' Star Danielle Spencer Was Hospitalized for Weeks Before Death

Danielle Spencer -- famous for playing Dee Thomas on the hit ’70s sitcom "What’s Happening!!" -- spent her final days in a hospital bed ... where she had to get food and medicine through an IV.

Danielle's mom, Cheryl Pelt, tells TMZ ... Danielle was hospitalized August 1 after a urinary tract infection turned septic, and she was unable to eat hard foods.

What's more, we're told Danielle had pneumonia in both lungs ... and she was losing weight and her gastric cancer was kicking up.

Danielle's mom says her family was with her Sunday in a Virginia hospital, and she was talking and alert.

The former child star's mother says Danielle suffered a "code blue" and was unresponsive ... doctors worked on her and found a pulse, and she was transferred to the ICU for more targeted treatment ... but her heart was weakening.

As we reported, Danielle died Monday at 60 years old. Her mother says she died of cardiac arrest and gastric cancer.

Danielle's mother says after her acting career slowed, she started working as a veterinarian in the Los Angeles area for over two decades ... which was always her dream after acting.

But we're told Danielle got sick in 2013 and she moved in with her mother at Cheryl's home in Virginia ...

Danielle's mom says her daughter suffered a long time ... she battled cancer, and there were long-lasting health complications from a severe car accident back in the day, which killed her stepfather, Tim Pelt.