Pepper plants can last a few years, with good care. Are you growing it indoors year-round? If so, maybe it’s not getting enough sunlight. Aim for 10 hours of direct sun each day, which is more than it needs when growing outside, the window absorbs and reflects a significant amount of energy. Without enough hours and intensity of sun, the plant will not flower and fruit well. Adding artificial light as a supplement helps.

Because it’s shedding leaves, I’ll also assume it has not been fertilized. Dropping leaves can also be caused by improper watering techniques, too small/too large a pot, very low humidity, spider mites (tiny dots on the leaf surface are dead cells sucked dry by the mites), cold soil or air temperatures. When watering warm season plants indoors in the winter, use lightly lukewarm water (about 85 to 90 degrees F). Peppers like air temps in the 70’s.

A picture of the plant would help! But for now, try this :

• Give it a lot more direct sun.
• Flush any excess salts through the soil by watering repeatedly with clear rainwater, if possible. Watering all the time with tap water gradually raises the soil pH, rainwater (more acidic) will stabilize pH if used now and then. Slope the pot in the sink (drainage hole at lowest point) so it will drain more thoroughly.
• Check the pot size. A fairly leafless plant should not be in a big pot. It runs a higher risk of being overwatered. You might unpot the plant, and see how much old soil falls away without any roots in it. Discard that soil outside. Find a smaller pot and some fresh potting soil, and repot it, keeping the soil surface at the same point on the stem as before.
• Keep the soil damp but not wet. Water all the way through the pot, but only after the top third of the root ball has dried.
• Check for spider mites and also for root mealybugs and root aphids. If insects have colonized the soil, starting over with a new plant might be the only option. Mites drown easily, so give the plant a good shower—tops and bottoms of leaves. Look for those telltale light colored pinpoint dots.
• Also check for diseases—brown roots, yellow spotting.
• A few weeks after it has recovered from the repotting, fertilize the plant with a soluble complete fertilizer. Use a more diluted concentration than is recommended on the label. Nitrogen, the major nutrient that plants need in the largest amounts, is mobile in the plant’s sap. As the plant struggles to keep its growing tip alive, it moves nitrogen from the lower leaves (that’s why they turn yellow and fall off) to the younger leaves.
• When the weather warms up (70’s daytime, 60’s nighttime), move the plant outside if at all possible. It will do so much better there.

I hope you can save it!