Hi there ~
I understand your concerns. I believe it would be a very bad idea to start smoking
marijuana again as you do have cravings and assuming that the urge to smoke is very high, there is a very high likelihood that you are physiologically and psychologically dependent on the drug - marijuana. I hope you consult a psychiatrist
who can give you alternatives when you crave marijuana. I am also glad that you are off of alcohol, but you would need to have been off of it after the surgery. I hope you continue the good work of not doing substances since it may be very harmful to your health especially after the surgery.
I hope this helps. Take care and have a lovely day!