I haven't used marijuana in 4 months and my parole officer gave me a drug test and it was positive what can I do?

It will be rather difficult, as the parole officer is going to rely upon the drug test. Regardless the fact that you may not have been actually personally using our one, if you have been in the presence of someone who is using, in the same room or in a car, you might well test positive. Being in such a situation would most probably be a violation of your parole as well.