It is a Chinese evergreen, botanical name Aglaonema and yes, it's in poor condition. These plants do not like any direct sun - yours appears to have some pink variegation, so it will appreciate bright daylight, but no sun - non variegated types will grow well in relatively darker situations.
The photo is not of sufficiently good quality to magnify in order to examine the leaves more closely to determine whether there is a pest or disease problem with the plant - you could examine the leaves and stems with a magnifying glass to see if it has anything such as spider mite which might be causing a problem.
I note you have the plant sitting in an outer container, and you say you water about every three weeks - it may be your watering regime needs changing. As with most plants, when the surface of the potting soil feels dry to the touch, but not so dry it's shrunken from the sides of the pot, a thorough watering should be done, allowing any excess to drain away freely from the base. Any outer pot or tray should be emptied 30 minutes after watering to ensure the plant is not left sitting in water.
Find a more suitable spot for it so that it does not receive sun, away from any heat sources, and water ongoing as described. The soil currently looks like it might be damp - if it is, wait till the surface has dried out a bit before watering again. You can also try giving it a feed with something like Baby Bio houseplant food, intended for use on foliage plants, but don't apply more often than once a fortnight or so, or according to the instructions on whatever product you use. Hopefully, it may recover. Further info on these plants and their care here How to Grow Chinese Evergreen Indoors.