If you're not sleeping well and wake up feeling tired, the problem may be that you're using an old or wrong-sized pillow. A poorly fitting pillow can cause neck and shoulder pain as well as snoring and sleep apnea. If you sleep on your side, consider using two pillows: 

1. one under your knees and 
2. one under your head.

How often should I replace my pillow?

There's no hard-and-fast rule about how often you should replace your pillows, but most experts recommend replacing them every two years. 

There are a few reasons why: 

• First off, as we mentioned above, pillows tend to lose their shape over time. 
• Second of all, the materials used in pillows can break down over time, especially those made from foam or latex foam, which means they won't support your head as well anymore.

Signs that I need to replace my pillow

Here are some other signs that indicate it's time for a new pillow:

• Pillow odour

If you notice a peculiar smell coming from your pillow, it may be time to replace it. A bad smell can be caused by mould or mildew, which will make you more susceptible to allergies and sinus problems.

• Body heat retention

The best way to tell if your pillow is too hot is by lying on it without clothes and feeling how warm it gets. If the pillow is retaining body heat, you might want to consider replacing it with a cooler one.

• Bulging or sagging of the pillowcase

If you notice that there are wrinkles in the pillowcase, then it's possible that the fill has shifted inside the case. This could mean that there's not enough support left in the fill or that it's time for a new one.

• Frequent fluffing of the pillow

When you notice that your pillows seem to need more fluffing than usual, then this may be an indication that they need replacing soon. Fluffing your pillows helps them maintain their shape and structure so they provide more support throughout the night.

• It doesn’t support your neck

Your head and neck should be supported evenly while you sleep on your side or back, but if one side of your face sinks into the pillow while the other side remains high above it, then that means that one side of your body is getting more support than the other, which isn’t effective at all.

Conclusion:-

All in all, it is not so difficult to tell when it's time to change your pillow, once you have paid attention to the signs it gives you.

First, whether material or natural, there is a limit to the number of times you can wash your pillow; too many washes will wear down its fibres and its filling. If you put your hand through the case and feel loose fibre, this usually means that washing is one time too many.

Second, at some point you should replace your pillow if your allergies make the nights uncomfortable—or if your snoring makes a lot of noise for those around you.