Tracy Jones, 40, had the procedure after her son Mark, then aged four, was diagnosed with inherited muscular dystrophy, which causes skeletal muscle weakness and the death of muscle cells and tissue.
She said she was advised to have the operation to avoid having another child with the condition, but was told it could be reversed on the NHS in future.
In February this year Mark, now 13, died after contracting pneumonia.
Jones from Tufley, Gloucester, said: "We had never heard of Mark's condition before and I was absolutely distraught. A lot of people were saying that I shouldn't have another child. I was stressed and confused.
"I should never have been making those kind of decisions in my state. At the time I was so upset about Mark's news."
Jones and her husband Neil Jones, 46, decided they would like another child, but have been told the NHS will not pay for the procedure and private clinics charge as much as £5,500.
Jones said: "I think he [Mark] would have liked a brother or sister to be honest, but having another child would not have been fair on them or him because he needed constant care at the time.
"I was told the operation was completely reversible and under no circumstances did anyone tell me that the NHS would not fund it.
"If I had been given all the facts at the time, I would never have gone through with it."
Jones, a cleaner, said it would take her and her husband at least three years to save up for the operation and she is worried time is running out.
She said: "There are women having babies in their 40s but we can't spend three years saving money for this. It needs to be done now.
"They said they would only do it in extreme cases but to me this is an extreme case.
"I do not want another child to replace Mark. You could never replace Mark, he was such a lovely boy. I just really want to have another child.
"I think the NHS should fund it. At the end of the day, the people making the decision aren't in my position and they don't know how it feels."
Decisions about whether patients are given reverse sterilisation procedures are in the hands of each county's NHS clinical commissioning group.
An NHS spokesperson said the treatment is not typically available on the NHS, but that decisions are made on a case-by-case basis.
According to official figures, just 72 female sterilisation reversal procedures were carried out on the NHS in 2012 to 2013.
In 2004 to 2005, when Jones underwent the sterilisation operation, around 400 reversal procedures were carried out across the country.
Jones is now hoping NHS Gloucestershire CCG will reverse its decision not to fund the procedure.
She said: "I know there are more important operations they need to fund first but at the end of the day there's nothing more important to me."
A spokesman from NHS Gloucestershire Clinical Commissioning Group said they were very sorry to hear of Jones' loss and sent their best wishes.
"Whilst the NHS does not routinely fund this procedure, our Patient Advice and Liaison Service would be happy to talk with Mrs Jones about her options," he said.