Welcome back, dongna
I was wondering why you ended up with a big all-channel antenna in your attic. Your previous thread tells the story of why:
Directionality of antennas
http://forum.tvfool.com/showthread.php?t=7131
The answer by ADTech seems to explain why your reception has changed.
The strength of the signals in the attic is most likely less than indicated on your report, but we don't know how much less because of differences in construction.
Before we could give any further advice, we would need to have some idea of the actual strength of the signals in your attic, and see some photos of your property and maybe even a satellite view of your house.
To protect your identity, you would need to give us your location or coordinates in a PM, but you might be willing to show us some photos in this thread.