I just took half of methadone and i have a drug screen on the 17th am i going to be clean by then?

Most likely: Methadone half life is up to three days, so you should be fine (unless you take more).

Probably: Clearance of substances from your body can be affected by a number of things: dose, metabolism, hydration, body type, chronicity of use, etc. On average, Methadone clears the body in 3-5 days (or 1-7 days) depending on the type of test and the study providing the information.