The doctor tested my blood for thyroid issues, do they find anything else and if so will they tell my parents

I may have lied to my doctor a little, ive smoked weed before and they did blood work but not for that im just wondering when they do blood work do they also test for drugs and other disorders? and if so will that be under confidentiality? i dont trust my doctor so im not being honest which is bad for me i know

Drug screening is not normally part of lab testing, unless the doctor might suspect that drug use is causing thyroid problems. If the doctor suspected drug use, he would have asked you about it when he had you in his examination room. Drug testing is also usually done via urine tests, they don't need to waste blood on that. The doctor probably bought what you said when you denied using them and is not considering it a problem.
Drug testing is added expense and it would also require more blood. So if they only took 1, 2, or even 3 of those little vials of blood, it wouldn't be enough to test for drugs.
If they do screen for drugs and actually find something, it must be kept under confidentiality, he should only talk to you about it first. But weed is totally unrelated to the thyroid, I wouldn't worry about it.