All the others no longer come in (ABC, NBC, PBS and a bunch of others). I refuse to go to having a box on my wall from the big two cable providers but they're pulling up all copper wires in my area so everybody has to make a choice, antenna TV or go with the biggies. Verizon has cut off anybody in my area who wants to keep a landline phone without having FIOS installed, same for the DSL internet service, it's gone. You have to get the box on the wall.
That sounds like either the tuner or the cables are internally degrading in some way. Or even the antenna, depending on what it is. A small outdoor antenna, if you can find a way to rig it up inside in some unobtrusive manner, will last almost forever. Of course, it will do better somewhat higher, outside, if the cable run is not long. Cables last longer indoors, too.
I’m overdue to replace my cabling, myself. Granted it’s been outdoors over 10 years.
Tree growth, new buildings (sometimes even at a bit of a distance), etc., can increase multipath (multiple signal reflections) problems, also.
For antennas, see Newark 30-2485. $25 plus shipping. 4.5 stars out of almost 5k ratings. Amazon has an RCA (brand) version for $41.74 including shipping. You could lay it on the floor of the attic, hang it just below the ceiling of a large closet or storage room, etc., as it is “flat”, if not using the wall mount. I have one 15 ft. above ground level and get stations 50-60 miles away IF it is pointed at them, 20-50 if not. (The latter will vary, as a strong multipath reflection coming in “on axis” may disrupt an otherwise usable off axis signal.) Experiment.
Simple yagi styles often work better than really fancy looking jobs. If you have room or will mount outdoors, both Newark 30-2370 and 30-2415 are good. Other models that mount at the rear of the antenna are easily damaged in high winds (but fine in attics if you have room.) “Bowties” are good in situations where you need good gain and less directivity, but are more subject to multipath distortions — in digital meaning the image will pixelate or drop out.
If that set is a smart TV, look into the firmware upgrades. It is possible to program the set to worsen the reception. Who would want to do that ? — the subscriber services like Netflix, hulu, etc. It is technically possible that this is going on behind your/our back.