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.
“With her being pregnant there were more complications. One was at 6-8 weeks and the other was just under three months.
“She almost died after one of the miscarriages because she got the flu, it was as simple as that.”
The miscarriages were put down to complications caused by Courtney’s diabetes and Lorraine said she feared she would never be able to have children but she fell pregnant again last year.
Lorraine said: “Because of what happened before, she had more information about what she had to do.
“She was very ill though and wasn’t well the whole way through her pregnancy. He was taking everything out of her. They had to deliver Declan two months early by Caesarean section.
“He was born with only one kidney, which might have been to do with being premature and he spent two months in hospital but he was fine.”
Lorraine, who lives with her partner Alan, said Courtney relished being a new mum and focussed all her energy into take care of her firstborn. The teenager had also recently moved into her first flat, in Penilee, with her boyfriend Declan, although the pair had fallen out in the week before her death and he had moved out.
Lorraine said: “The last time I spoke to her was on the Tuesday night, online. She had said she was feeling a wee bit peely wally. She had had a cold.
“I said to her to phone the diabetes nurse and she sent me pictures of Declan and that was it.
“We were emailing her and texting her the next day and hearing nothing and it wasn’t like her. She hadn’t been on Facebook and she was on every day posting pictures of the baby.
“I just had this terrible feeling. I said to my daughter, phone the police and she told me she was already at the flat and there was no answer and she couldn’t hear the baby.
“Then I said, just call the police. There is obviously something wrong. I was at the flat and there was ambulances and police but they wouldn’t let me in.
“They said she was there for two days and nobody knew she was there.
“She was lying on the couch with a cover over her and her Lucozade and insulin next to her. The police were really good, they changed Declan’s nappy and gave him some milk.
“They kept him in hospital for two days for observation but he was fine.
“It just came out of the blue. All we know is that she was there for two days.”
The family are waiting for the results of more detailed tests, which will take six weeks, after the post mortem failed to shed any light on the cause of Courtney’s death.
Lorraine, who is known in the community for her fundraising work, said: “They did say that if it was something related to the diabetes it would show up in the post mortem but there was nothing there.
“They had changed her insulin so many times.We don’t know though.”
The family are now planning Courtney’s funeral with baby Declan being cared for by Courtney’s sister Lorraine, 26, who has two children.
Lorraine’s son Jordan, 23, is a tattooist, and she is planning to get a tattoo of Courtney’s fingerprint.
She said: “She was just a normal teen, dead bubbly. She had loads and loads of of friends, she was very popular.
“Last week, she had dyed her hair purple and it had turned orange and she was laughing about it.
“Declan was like a miracle baby to her. If you look at her Facebook page, it was just baby, baby, baby.Every single day, every minute of the day.
“Declan is one of those babies who is always smiling. He’s just started to giggle now. We’ve got to keep going for his sake.”
A Facebook fundraising page has been set up to help the family with funeral costs called RIP Courtney, Fundraising for Lorraine Newlands.
For advice and support about diabetes go to www.diabetes.org.uk ENDS