+1. An amplifier will reduce the number of stations you receive, regardless of whether the antenna is indoors or outside, because of overload. You have a uniquely strong signal environment. Any one of the first nine stations in the TVFool report is powerful enough to overload an amp/booster!
Did you have strong video ghosts on analog TV, before hooking up the converter? That's multipath interference, and like overload, it can totally bock digital reception. A more directional antenna would combat this problem.
A lot less antenna could fix this problem. This is a situation of signals above 70 NM.
This means they are so strong anything is an antenna.
Sojo, try this for an experiment and probably a solution. Find some thin solid wire. If you know wire sizes 18 to 22 gauge is perfect. Cut a piece about 15 inches long and try just putting the end of it in the antenna in connector where you screw on the antenna. If you have extra coax you could just cut a 15 inch piece and strip off the shield leaving just the center conductor also. You may even find a short piece works better.