I smoked weed once a month ago (and exposed to 2nd hand smoke for 30minutes between 2 separate occasions that were 3 days apart). will i test positive?

No, should be fine: You don't say when you were exposed to secondhand smoke but secondhand smoke exposures are unlikely to cause positive tests unless very recent and extensive. For smoking only once it is unlikely that a urine test will be positive for longer than a week. See http://www.ndci.org/sites/default/files/ndci/THC_Detection_Window_0.pdf for much more detail if you wish.