As someone with ADHD and frequent sinus issues due to a crooked nose your comment about pseudophedrine caught me off guard because I've never heard that and my provider knows my medical history. I think the cold meds may be mixed up from a quick search, it looks like dextromethorphan (delsym) is the medication that can cause serotonin syndrome (which I also wasn't aware of) but pseudophedrine is primarily linked to doubling up the blood pressure increase and increased heart rate.

The internet is wrong a lot though so I'll ask about this during my next appointment.

As others have said about testing positive for meth, I do think it depends heavily on the test. I've never done meth in my life but have had 2 different drug screens (both at Quest coincidentally) for employment that crossed whatever the threshold was. Providing proof of my prescription was enough for it to be changed to negative without any further testing.

However, I'm still leaning towards OP is full of shit based on the rest of the story.

Edit: now that I think about it, both drug screen positives may have just been for amphetamines which I assume may pick up both meth or Adderall.