Unreliable pregnancy test

Yes, unfortunately, that could indicate a threatened miscarriage. Then your hCG goes down. Very sad.
It could also be that you've drunk a lot and your urine is so little that your hCG shows less on the test.

I hope and wish for you the second scenario.

Good luck. P.S. If not, have a blood test done and repeat it in two days so you can see if it's rising or falling.

That's true. I think it's also mentioned in the leaflet. It can indeed be due to more or less concentrated urine. Just test again in 2 or 3 days.

Had exactly the same 3+ a few days later 2-3. It really depends on your urine. I'm already 11 weeks again.