Courtney Newlands, 19, lay in her flat for two days before police broke down the door prompted by her anxious family.
They found the young mum lying on the couch with baby Declan beside her in his cot.
Courtney’s mum Lorraine and sister, also Lorraine, 23, had become concerned because they had not not heard from the teenager, as the close family spoke every day.
It is thought that she may have suffered complications from Type 1 diabetes, caused by the pregnancy.
But so far tests have not given medics any definite clues about the cause of her death, which is thought to have happened between February 19 and February 20.
Declan was rushed to hospital and kept in for two days after being treated for dehydration but is now at home, being cared for by Courtney’s sister Lorraine.
Lorraine, 43, who lives in Pollok, Scotland, said: “I think it’s affecting us more because we don’t really know what happened.
“They way we are looking at it, is, if it had been one more day would Declan be here?
“It’s a shame because he was crying the other day and I played a video of Courtney and he just stared at her phone. He stopped crying straight away.
“We are going to keep playing them because it will make him feel as if she’s still there.”
Courtney was diagnosed with diabetes when she was four. Lorraine says she phoned the hospital four times after becoming concerned about her daughter’s symptoms.
She said: “You know yourself that something is wrong. She wasn’t getting up and her eyes were rolling in her head.
“I rushed her down straight way and as soon as we got there she collapsed.
They had to hook her up to machines. I’m lucky I got her there.
“It was hard for her after that. Everyone thinks that diabetes is easy but it’s not as easy as what people think. You have to do daily checks, you can’t eat or drink what you want. I think you need to have a family member with it to understand.
“I managed it for her but it was more in her later years that it affected her. She fell pregnant and had two miscarriages, last year and the year before that.