I need a sanity check (my last one bounced.

)
I live in West Georgia. I am about 40-50 miles from the major transmitters. They are all at about the same compass heading. Recently I started having problems getting 46 (which according to TV Fool should be one of my better stations). If I turn to get 46 better, I start losing 5 (and they both should be at the same compass heading). I was getting 8 and 30 with no problems and now they are gone.
I have an 10 year old Channel Master antenna (the big one for VHF/UHF) with a preamp mounted outside my house at a height of about 20 feet above the ground.
Do I have too much antenna, not enough, not high enough, or too old? Any recommendations from our learned group on the forum? I have tried turning it every way possible and if I get one station, I lose another. Turning the antenna directly toward Atlanta causes 46 to go away. I can't get 46 to come in at more than 65% (note that 11 and 2 will come in at around 98%).
Thanks for your help in advance.
Big Al.