When you think that your childs addiction is 'your' fault, Take a look at or read the book "A child called It" and ask yourself why He doesn't have an addiction to drugs. You can be THE WORST, ABSOLUTE WORST MOTHER who abuses your child to where they should not be alive and they can grow up to be a child activist and best selling author or you can be the best mom in the world and they can grow up to be an addict.
You don't get to decide which, unfortunately. In turn you don't get to take blame. You can only do the best you can.