I had the same problem off and on theu my teans and 20s. Weight loss and food choices help.

The only "natural" ways that have been advised were weight-less if you are overweight. Lots of water and herbal tea such as chamomile. Exercise.....Sex...

Remember everyone's body is different and some or none of these may not work. Other factors going on in your life such as stress can also increase the duration of your period especially when have PCOS. I would reach out to a doctor if this continues.