Sorry this happened to you and your son. Do you live in British Columbia as your profile name suggests? If you lived in the Toronto area I would suggest contacting the Barbra Schlifer Legal Clinic. They specialize in assisting marginalized women and victims of abuse. From your story I think (and hope) you do not fall into those categories but given that you are a single mother, there is a chance they would be in a position to help. If you are not around here, I still suggest searching for a similar clinic or perhaps asking the Schlifer clinic where they think you should refer to in your area to seek advice. Here is their website:
https://schliferclinic.com/legal-services/immigration-and-refugee-law/
It is difficult to find the best answer on any online forum. There are generally two reasons an H&C case is refused: 1. the case is not compelling 2. the case is not well presented.
Without knowing much about your case I could only comment that: In the case of a medical issue, you will still need to prove there is urgency beyond the usual medical need and that the hardship involved is not transitory and is likely permanent. The medical need per se is unfortunately viewed as a negative factor (due to the extra burden on health services). Therefore, the hardship you would face if they asked you and your son to go back and apply from outside Canada should clearly outweigh that negative factor. If you think these hold true for your case, it could be that your haven't demonstrated your point in your application and a new application, aided by legal advice is the way to go. This is an important decision because it would involve a long period of waiting, especially as you would be (or maybe you are currently) out of status and at risk of removal.
Lastly, another forum user suggested changing your province. That would not help at all. These cases are federally adjudicated and place of residence has no independent role in the outcome if you live outside Quebec.