I am a seventeen-year old boy who has been smoking marijuna weekly for 4-5 months. I recently became aware that I have many symptoms of thought disorder, such as distractability, tangentiality, illogicality, neologisms, persistent repetition of words, and echolalia. Do I have schizophrenia?
I don't know if you have schizophrenia but you certainly seem to have a good knowledge of schizophrenia.
For someone who thinks he may have symptoms of thought disorder, your thinking appears quite clear.
Given that, you are clearly a smart young man, so you probably know that smoking marijuana is not a good idea for someone experiencing such symptoms. So if you can give it up, you should.
To determine if you have schizophrenia or may have symptoms which are consistent with risk for schizophrenia, you can have an evaluation at one of many "prodromal" or "high risk" programs. www.schizophrenia.com has a list of centers worldwide which can do diagnosis and treatment relevant to risk for psychosis and schizophrenia.
The phenomena you describe may also have a "neurological" basis, so a good physical exam with neurological testing would also be indicated.