Welcome to HCM
We understand your concerns
I went through your problem description. I suggest you not to worry. The answers to your questions depends on so many things like, period of drug use, quantum of use, which is the substance and your mental state and resolve, and willingness to quit and of course family support.
There re several methods of treatment starting from simple counseling to drug rehabilitation
therapy. There may not be any withdrawal symptoms
if the habit is not that old and in case of some of the substances.
Instead of worrying about 'what will happen next', you should go your ground and stop it once for all. See what is coming, and if it is required, then go for rehabilitation treatment.
Hope this answers your query. Available fo further clarifications.