Failed pre-employment drug test, and employer ordered a second one instead of rescinding offer. What does this mean?

I took a drug test yesterday 100% sure I would pass cause I don’t do any drugs or take any medications. I got an email today from my employer saying I failed, and that they need me to take another test within three days.

My boyfriend smokes medical marijuana (I don’t) but he does it in the house. I read secondhand marijuana smoke can cause a false positive so I’m hoping that’s all it was and I’ll pass this time.

But I read that typically an employer won’t order a second test, but just rescind the offer. My question is, does the fact that they ordered another test mean they suspect it’s a false positive? Also, will a re test be a different kind of test, maybe one that’s more accurate in the off chance that the first positive was false? Like a more sophisticated test that can differentiate between what causes false positives and actual drugs? I don’t know how this works but I’m freaking out and not only do I really need this job, I actually WANT it and was excited about starting and now I’m crushed at the prospect of not getting it. What does this mean? And what should I do?

Any and all advice is appreciated. I’m ignorant about this stuff and emotionally I’m at a loss.

Edit cause I forgot to add my stats: 27F, 5’7, 140ish lbs

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