I'm just playing devils advocate because after reading this thread I retested and my tests are still also a very strong posistive 2 weeks after my miscarriage.
These tests will show a strong posistive at anything about a 25 hcg. Whereas your hcg levels should drop by half after a miscarriage every 48hrs, it doesn't always happen for everyone.
If your miscarriage has been confirmed by a scan, it's unlikely that they were wrong but if you have had unprotected sex since then then it's quite possible that another baby has started forming with a low hcg and you still have some hcg left from previous pregnancy.
I do hope that the doctors are wrong and you have a miracle baby hanging in there.
As I said, I miscarried 2 weeks ago, still strong bfp and my AF showed up today. I am hoping that once AF has finished then my tests will go back to negative. But we'll have to see xxx