Physical at doctors coming up, need advice....?

Drug testing is never part of a regular work up. Its only done in cases where you're sick and the hospital needs to know if the symptoms can be drug related or if there is a court order to be tested. Your parents can request one but you are under no obligation to take it if they do. In NC You're considered a reasonable person capable of refusing any medical attention you don't want. The only reason I cold see that you should tell your doctor is if he is prescribing you any medications. He needs to know then. For example certain anti biotics can have an adverse effect when combined with THC. And schizophrenia meds (which you shouldn't be on but its just an example) can actually make the symptoms worse if mixed with THC. However, if you feel this guilty about it and this worried about it maybe you should quit smoking??