Zithromax is the brand name of a single macrolide antibiotic; azithromycin. (not a "group of drugs") It will not cause you to show positive on a toxicology screen. Marijuana is the likely culprit, the pregnancy is non contributory. (but please, don't smoke pot when you're pregnant).

No. Strattera is atomoxetine. It is a stimulant, but is not a controlled substance and is will not show as a positive for any amphetamine (including methamphetamine) or metabolite.