A good mattress matters for sleep, but experts say a good pillow could be just as important.

A pillow that doesn't support your head well can cause muscle tension in your neck and shoulders, experts say. That tension can even lead to a headache in the morning.

"If your pillow is not really supporting your body, your head very well, that can cause muscle tension. It can cause those muscle fibers in your neck and your shoulders to be stretched or placed in an awkward position," sleep specialist Dr. Brian Chen said. "And that can even cause like a muscle tension headache in the morning, and it can go against what you're trying to do of getting good rest."

Experts say most pillows need to be replaced within a couple of years. The material tends to give out after a while, and you don't get the same support.

You can check if your pillow has a dent or is lumpy. You can also try the pillow fold test: if you fold it together and it bounces back, that's a good sign. If it stays folded or goes flat, it's probably time to get a new one.

"If you're struggling, if the pillow is already too bad, it's worn out, then it is definitely time to reinvest in yourself and get a nice pillow," Chen said. "And just keep in mind, again, when you're shopping for pillows, it's not 'more expensive is better.' It's what fits your body. What do you need? What's going to help you sleep?"

If you still notice discomfort after getting a new pillow, you may want to talk to your doctor. There may be another issue that needs to be taken care of.