There is something wrong with my peace lily.

Its always been a big flourishing plant since I bought it from a plant store 3-4 years ago. Its in a big tall black plastic pot but that pot is in a wider ceramic pot to catch the water (the ceramic pot is too short to house the plant on its own.) I haven't changed the pot because I just don't seem to find pots that are large enough that I actually like.

I water it once a week. I periodically let it dry a bit more but as soon as I see it start to wilt, I give it a good watering. I don't give it Miracle Grow often- maybe once or twice a year. Its been about 4 months or more since the last time.

About two-three weeks ago, I noticed some of the leaves were turning yellow, then brown and it was wilting a bit. i gave it water, then the following week, I figured I had not given it enough water so I gave it more and I cut off all the brown or yellow leaves. Now over the last week, it is almost totally wilted and there are multiple yellow leaves. I touched the soil- its still lightly moist so it doesn't actually need water. I don't think its too close to the sun- its in the corner of my living room with a window about 4 feet to the left of it.

I loved this plant but I think its dying! Any help on what to look for and do?

Thanks