@Electron's suggestion to test reception with the antenna outside the building is reasonable. If the results are good, an outdoor antenna can be suggested.
@Tower Guy's suggestion re. an FM-trap is also very reasonable. In addition to the product link already posted, Radio Shack store are also a source for an FM-trap (
RS Catalog# 15-024). There is one major caveat however, an FM-trap will be of little use if used with an antenna with a built-in amplifier... which TG has already pointed out.
Here's a copy of the RCA ANT-1251R user manual from the manufacturer's web site.